Dynomite

This thread includes various modifications/refurbishments of several corvettes including three 1990 ZR1s, one 1991 ZR1. one 1995 ZR1, and one 1990 L98 corvette.
The various modifications and refurbishments are described in detail with complete photo coverage for each corvette.
Some duplicate modifications are included with different photo coverage and details
Each of the six corvette coverages starts with a complete detail summary of modifications and refurbishments.

Individual Corvette modifications/refurbishment SUMMARY
Post 62 -1990 (#2067) LT5 Top End Rebuild (C5 Z06/Wilwood Brakes, SW Headers, Aluminum Radiator)
Post 76 - 1991 (#1427) LT5 Rebuild (C5 Z06/Wilwood Brakes, SW Headers, Ron Davis Radiator)
Post 119 - 1990 (#3032) LT5 Top End Rebuild (Fluidyne Radiator)
Post 133 - 1990 (#0072) LT5 Top End Rebuild (Ron Davis Radiator)
Post 230 - 1995 (#0186) LT5 Specific Top End Rebuild (C5 Z06/Wilwood Brakes, Fluidyne Radiator)
Post 261 - 90’ (#8550) Corvette (L98) Modifications (SW Headers, Wilwood Brakes, Ron Davis Radiator)

The 91' ZR-1 (LT5) Modifications/Rebuild Tricks starts with post 76 (Including 500+hp).
See Section C and Section E Below for specific details related to the 1991 ZR1 modifications.

The individual corvette discussions is followed by specific technical information associated with all ZR1 corvettes.

Any word or group of words underlined are Left Clickable Links

A. See Technical Index which is an INDEX of Technical Posts in this thread.

A Specific Technical INDEX is provided at the bottom of this post recognizing the Index of this Thread in A above is mostly Date based and topics created as ZR-s/LT5s were Restored/Modified. This Specific Technical INDEX (BELOW in this Post) includes ALL posts in this Thread.


B.The Solutions index is an index for Corvette Technical Posts including those Posts in the C4 ZR-1 Discussion Section and specific posts in this thread.

Post 102. SOLUTIONS Overview and Ebay Searches
Post 103. ZR1 General
Post 104. ZR1 Electrical
Post 105. ZR1 Engine
Post 106. ZR1 Drive Train
Post 107. Awesome
Post 108. ZR1 Engine Fuel, Lubrication, Cooling, and Exhaust
Post 109. ZR1 Specifications, Restorations, Air, Audio, Lifts, and Road Trips
Post 110. ZR1 Engine (LT5) Bolts and Hydraulics

C. See LT5 Specific Rebuild Tricks which includes complete photo coverage of an LT5 Rebuild including engine removal and installation in this thread.

D. Related other threads found in the C4 ZR-1 Discussion Section are as follows:

Tech Info - LT5/ZR-1 Technical Calculations LT5 Technical Calculations
Tech Info - LT5 Eliminated Systems LT5 Eliminated Systems
Tech Info - Marc Haibeck on LT5 Eliminated Secondaries and Associated Anomalies
Marc Haibeck on LT5 Eliminated Secondaries and Associated Anomalies
Tech Info - LT5 Added Systems LT5 Added Systems
Tech Info - Removing a Pressed In Fitting Removing a Pressed In Fitting
Tech Info - LT5 New Rebuild Issues (Lifters and Camshafts) LT5 New Rebuild Issues (Lifters and Camshafts)
Tech Info - LT5 Timing Chain and Engine Pulses LT5 Timing Chain Calculations
Tech Info - LT5/ZR-1 Technical Calculations LT5/ZR-1 Technical Calculations
Ben's 90' Complete Restoration including the rebuild of an LT5 bottom to top Ben's 90' Restoration

HELP threads:
For additional Help Posting Photos Creating Albums and Posting Photos
For additional Help in creating Posts using Link References Reference Link Names

E. Overview of ZR-1 (LT5) Modifications/Rebuild Tricks (500+hp)



1. Systems added included LT5X Head Studs and an Oil Catch Can for the PCV system.
2. Several systems were eliminated including the secondaries, TB coolant, Air Injection system, and Vacuum system.
3. LT5 engine was highly ported top end with reground camshafts installed.
4. Included in this thread are the modifications of a 90' Corvette (L98).

1. LT5X Studs (Randy Woods)........................................ ...2. 200 Amp Alternator

3. Eliminated Systems (Secondaries)............................4. Plenum, TB Coolant eliminated


5. Reground Camshafts (Pete)...........................6. Air Horn, Plenum, IH, Head Porting (Locobob)


6. Specific Technical INDEX presently being created
Post 280 - Specific Technical Index

7. Technical Index Post Updates
Post # ………………………..Date

Last UPDATE of post 1 Feb, 2024

Dynomite

Technical Index

INDEX of Technical Posts for ZR-1 (LT5) Modifications/Rebuild Tricks.
Left click on any Link Name as described below.

This Index is organized by Headings from General Information (Posts 3 - 6) to Engine Cooling (Posts 7 - 14), Lifting (Posts 15 - 16), Lubrication (Posts 18 - 20), Camshaft Timing (Posts 21 - 28), Top End Restoration (Posts 29 - 34), Transmission (Posts 35 - 39), Drive Train & Brakes (Posts 40 - 44), Exhaust System (Posts 45 - 47), Electrical/MISC (Posts 48 - 59), Audio (Posts 60 - 61), 1990 LT5 Specific Rebuild Tricks (Posts 62 - 69), Bling and Performance (Posts 70 - 75), 1991 LT5 Specific Rebuild Tricks (Posts 76 - 96), TIPS (Posts 97 - 99), Tools and LT5 Differences (Posts 100 - 101), Solutions (Posts 102 - 110), Ebay Searches and Acronyms (Post 111), Additional Information (Posts 113 - 117), Miscellaneous Topics (Posts 118 - 130), Forum Albums and Resizing Photos(Posts 131 - 132), Other Topics (Posts 133 - 140), Questions and Answeres (Posts 141 - 145), LT5 Eliminated and Added Systems (Posts 146 - 148), LT5 Systems (Posts 149 - 180), 1991 LT5 Spare Engine Rebuild/Assembly (Posts 181 - 200), ZR-1/LT5 Technical Calculations, (Posts 201 - 215), Eliminated Systems and Added Systems (Posts 216 - 220), LT5 Lifters, Camshafts, and Valves (Posts 221 - 229), 1995 Top End Restoration (Posts 230 - 250), Summaries (Posts 251 - 260), Standard Corvette (L98) (Posts 261 - 280).

Individual Corvette modifications/refurbishment SUMMARY
Post 62 - 1990 (#2067) LT5 Top End Rebuild (C5 Z06/Wilwood Brakes, SW Headers, Aluminum Radiator)
Post 76 - 1991 (#1427) LT5 Rebuild (C5 Z06/Wilwood Brakes, SW Headers, Ron Davis Radiator)
Post 119 - 1990 (#3032) LT5 Top End Rebuild (Fluidyne Radiator)
Post 133 - 1990 (#0072) LT5 Top End Rebuild (Ron Davis Radiator)
Post 230 - 1995 (#0186) LT5 Specific Top End Rebuild (C5 Z06/Wilwood Brakes, Fluidyne Radiator)
Post 261 - 90’ (#8550) Corvette (L98) Modifications (SW Headers, Wilwood Brakes, Ron Davis Radiator)

GENERAL
Post 3 - LT5/ZR-1 Fluids
Post 4 - General Bolt Length, Bolt Torque, Loctite, and Tools
Post 5 - Use of thread Lubricants, Loctite and Sealants
Post 6 - Manual Supplement, Secondary Diagnostics, Sensors, and Prom Codes.

ENGINE COOLING
Post 7 - Thermostats, Fans, Water Pump, and Radiators
Post 8 - LT5 Radiator and Initial Coolant Fill Tricks
Post 9 - HVAC Temperature Display And Radiator Efficiency Test Runs
Post 10 - Water Pump, Coolant Temperatures, and Coolant
Post 11 - Radiator Debris Screens
Post 12 - Getting The Air Out of the Coolant System
Post 13 - TB Coolant Discussion
Post 14 - Coolant Characteristics (Mix, Pressure, Elevation)
Post - Eliminated TB Coolant Photos and Details

LIFTING
Post 15 - Lifting The LT5
Post 16 - Lifting and Towing the ZR-1
Post 17 - Kudos

LUBRICATION
Post 18 - Engine Lubrication System Functional Discussion
Post 19 - LT5 Lubrication Tricks and Replace Dip Stick Handle
Post 20 - Potential Oil Leaks and the OPRV Cover Plate

CAMSHAFT TIMING
Post 21 - LT5 Camshaft Specifications and Camshaft General Timing (pinning)
Post 22 - LT5 Camshaft Specific Timing (degree wheel)
Post 23 - LT5 Camshaft Timing Additional Tricks
Post 24 - LT5 Timing Diagrams and Timing Chain Effective Lengths
Post 25 - LT5 Timing Chains and Sprockets
Post 26 - Setting/Installing the Chain Tensioners Tricks
Post 27 - Cam Cover Installation Tricks
Post 28 - PCV system (Need for Oil Catch Can)

TOP END RESTORATION
Post 29 - Plenum Pull
Post 30 - LT5 IH (RC Injectors), Fuel Rails, Plenum Install Tricks
Post 31 - Vacuum Systems 90' and 91' (Secondary and Cruize/HVAC)
Post 32 - Eliminated IH Housing and Throttle Body (TB) Coolant system Tricks
Post 33 - Eliminated Secondary Throttles/shafts Tricks
Post 34 - Stainless Steel Air Box and Air Filter (L98 and LT5)

TRANSMISSION
Post 35 - Pilot Bearing
Post 36 - ZR-1 Transmission Install and Lift Tricks
Post 37 - Vibration Issues Diagnosis
Post 38 - Throwout Bearings and Clutch Forks
Post 39 - C4 Beam Plates and Installation

DRIVE TRAIN AND BRAKES
Post 40 - Tires and Selective Ride Control
Post 41 - ZR-1 (90' and 91') Wilwood Rotors and C4 to C5-Z06 Conversion
Post 42 - Going from 3:45 to 4:10 Differential
Post 43 - LT5 Final Inspection including, Testers, Brake Tricks
Post 44 - Accessories

EXHAUST SYSTEM
Post 45 - Exhaust System Replace with Headers
Post 46 - Exhaust Headers Locking Bolt Tricks
Post 47 - Installing the LT5 with Headers and the O2 Sensors Functionality

ELECTRICAL/MISC
Post 48 - 1990 and 1991 Fuses/Additional 12V Connector
Post 49 - Backup Tail Light Switch and Alternators
Post 50 - Replacing the Windshield and Wiper Motor
Post 51 - CMHSL LED, Full Power Key and Alternator Pulley
Post 52 - Starter, Starter Relay, Wiring Harness, Battery, and Plugs Tricks
Post 53 - Electrical Ground Connections and Installing Starter Relay
Post 54 - Ignition Key Codes and Clearing 1990 INFL REST Codes
Post 55 - ALDL Fault Code Reader/Eraser
Post 56 - ABS, Ride Control, CCM, SIR Code Definitions
Post 57 - ZR1 90'-95' ECM Interchangeability and CODES 90' TO 92'
Post 58 - Recharging The AC System
Post 59 - Crankshaft Sensor and Camshaft Sensor

Audio
Post 60 - Bose Speaker Amp Options TIPS
Post 61 - Typical Low Mileage ZR-1 Restoration Starting With Audio

1990 (#2067) LT5 SPECIFIC TOP END REBUILD TRICKS
Three 1990 Top Ends were rebuilt and best tricks linked here
UL LOSE, UWLNTWN, ULNOTWN
Post 62 - 1990 (#2067) LT5 Top End Rebuild (Including Wilwood Front Brakes)
Post 63 - Removing Plenum (including the 10 minute Plenum Removal)
Post 64 - Inspection, Testing and Reconditioning the Valley, Starter, and Coils
Post 65 - INFL REST grounds and Alternator Connector Boot
Post 66 - Secondary Functional Test and Reconditioning the Secondary Actuators
Post 67 - Removing Cam Covers (Engine In Car) for Inspections of Camshafts
Post 68 - Eliminating TB Coolant and Air Induction, Added Oil Catch Can and Painting
Post 69 - Summary of 90' Reconditioning/Modifications

BLING AND PERFORMANCE
Post 70 - Bling (Carter and Others)
Post 71 - 1991 ZR-1 (LT5) Performance
Post 72 - 1991 ZR-1 (LT5) Modifications (500+ HorsePower)
Post 73 - Summary of LT5 Restorations
Post 74 - What Fluids to use in the ZR-1
Post 75 - 1990 ZR-1 (LT5) Performance/Reconditioning/Modifications

1991 LT5 SPECIFIC REBUILD TRICKS
Post 76 - 1991 (#1427) LT5 Rebuild Tricks
Post 77 - New Piston Sleeve and Piston
Post 78 - Timing Chain Guides Installation
Post 79 - Timing Chain Idler Sprocket Lubrication and Installation
Post 80 - Front Cover, OPRV Cover, Water Pump, Harmonic Balancer
Post 81 - Oil Pan (Oil level and Knock Sensor), Flywheel, Clutch, Bell Housing
Post 82 - Checking for Oil Leaks/Making your own SS Braided Oil Lines
Post 83 - Installing Heads and Camshafts
Post 84 - Camshaft Timing
Post 85 - Camshaft Timing (Locking the Camshafts) and Camshaft Lubrication
Post 86 - Cam Covers (Filters and Wear Strips)
Post 87 - Installing Headers and Exhaust
Post 88 - Installing Engine In ZR1
Post 89 - ECM Chip and Other Electrical Connectors
Post 90 - Alternator, AC Pump, Power Steering Pump
Post 91 - Installing Fuel Rails and Ignition Coils
Post 92 - Installing Plenum, TB, and Air Cleaner
Post 93 - Filling With Coolant and the Air Locked Water Pump
Post 94 - Preliminary Starting Checks
Post 95 - Engine Running First Time Checks
Post 96 - Summary of 91' Reconditioning/Modifications

TIPS
Post 97 - Checking for abnormal noise and leaks LT5 engine
Post 98 - Number 8 Spark Plug Removal and Test Drive with Jeff Gordon
Post 99 - Adapting 91 IH to 90 Heads

TOOLS AND LT5 DIFFERENCES
Post 100 - ZR-1 and LT5 Tools
Post 101 - Differences between 90', 91' and 95' ZR-1s and Engines

SOLUTIONS
Post 102 - SOLUTIONS Overview and Ebay Searches
Post 103 - ZR1 General
Post 104 - ZR1 Electrical
Post 105 - ZR1 Engine
Post 106 - ZR1 Drive Train
Post 107 - Awesome
Post 108 - ZR1 Engine Fuel, Lubrication, Cooling, and Exhaust
Post 109 - ZR1 Specifications, Restorations, Air, Audio, Lifts
Post 110 - ZR1 Engine (LT5) Bolts and Hydraulics
Post 111 - Ebay Searches and Acronyms
Post 112 - Kudos

ADDITIONAL INFORMATION
Post 113 - Fuel Trim and Closed/Open Loop Operation
Post 114 - Kudos
Post 115 - Question Regarding Air Locked Water Pump
Post 116 - LT5 Air Locked Water Pump Simplified
Post 117 - LT5 PCV System

Miscellaneous Topics
Post 118 - Three Things To Do For A No Start
Post 119 - Last 1990 (#3032) ZR-1 Sold and ZR1 Inspection TIPS
Post 120 - Thermostats, Fans, Radiators and Coolant Filling
Post 121 - Finding A Vacuum Leak
Post 122 - Wilwood C5 Z06 Brake Conversion with Sawblades
Post 123 - Rebuilding Belt Tensioner
Post 124 - Checking Lubrication System
Post 125 - SS Braided Oil Cooler Hoses and Fittings
Post 126 - Getting The Air Out Of Coolant System
Post 127 - Replacing Bolts In Various Components and Use of Loctite
Post 128 - Activating Secondaries
Post 129 - Engine Has To Be Pulled To Time Camshafts
Post 130 - Cam Cover Filters

FORUM ALBUMS AND RESIZING PHOTOS
Post 131 - Resizing Photos for Forum Posts and Creating Reference Links
Post 132 - Using Forum Photo Albums……Resizing photos

Other Topics
Post 133 - Minimum Restoration of a 1990 (#0072) ZR-1
Post 134 - Continued........Minimum Restoration of a 1990 (#0072) ZR-1
Post 135 - Replacing the Heater Core and Heater Hose Connection
Post 136 - Hose Clamps, Screws/U-Nuts, Magnetic Sockets
Post 137 - Using Permatex and Headliner Glue
Post 138 - Showroom Mats for ZR-1s
Post 139 - Bose Speaker Amps and CDM Replace
Post 140 - Cylinder Numbers and Firing Order

Questions and Answeres
Post 141 - Exhaust Hangers Question
Post 142 - Exhaust Hangers Defined
Post 143 - Kudos
Post 144 - Replacing the Coolant (LT5)
Post 145 - how often do you change your oil and other fluids

LT5 Eliminated Systems
Post 146 - LT5 Eliminated Systems

ZR1 Added Systems
Post 147 - ZR1 Added Systems including Differential Case Drain
Post 148 - Elite Engineering Oil Catch Can

LT5 Systems
Post 149 - Engine with bottom end intact
Post 150 - How to Remove Injector Housing Coolant Manifold Torx-30 Bolts
Post 151 - Starter Rebuild
Post 152 - Clutch Master and Clutch Slave Cylinder
Post 153 - Spark Plug Wire Separators
Post 154 - The Battery Disconnect Switch and Having an Operational Secondary Full Power Switch
Post 155 - Six things I ALWAYS do on any LT5.
Post 156 - Replacing the Serpentine Belt
Post 157 - LT5 Engine Cooling Issues on Hot Days
Post 158 - LT5 Engine Optimum Operating Temperatures
Post 159 - Checking Camshaft Timing Engine In Car
Post 160 - PCV Upgrades
Post 161 - Secondary Chain Guide Rattle
Post 162 - Cam Cover Chain Guides, Filters, and A136
Post 163 - Camshaft Identification
Post 164 - MSD 8224
Post 165 - Painting Top End
Post 166 - Battery Disconnect
Post 167 - 1990 and 1991 Plenums and TB Coolant Blocking at IH
Post 168 - Installing a Ron Davis Radiator and Testing
Post 169 - Reserved 21
Post 170 - Abbreviations
Post 171 - Reserved 23
Post 172 - Reserved 24
Post 173 - Reserved 25
Post 174 - Reserved 26
Post 175 - Reserved 27
Post 176 - Reserved 28
Post 177 - Reserved 29
Post 178 - Reserved 30
Post 179 - Horsepower Losses from Angular Acceleration of Rotational Mass
Post 180 - Tools to Carry in the ZR-1

1991 LT5 Spare Engine Rebuild/Assembly
Post 181 - The Rebuild and Assembly of a 1991 Spare LT5
Post 182 - Bottom End Restoration Including Oil Pan
Post 183 - Starter Rebuild
Post 184 - Restoration of the Ignition Coils, plugs, Wires
Post 185 - Painting Plenum, TB, Injector Housing and Cam Covers
Post 186 - Restoration of the Secondary System including the linkages
Post 187 - Restoration of the Injectors
Post 188 - Restoration of the Heads
Post 189 - Head Installation
Post 190 - Finding TDC and Locating 51 deg BTDC
Post 191 - Water Pump, Power Steering Pump, and Injector Housing Installation
Post 192 - Injector Housing TB Coolant Blocking
Post 193 - Alternator and AC Compressor Installation
Post 194 - Camshaft Timing
Post 195 - Installation of the DIS Module
Post 196 - Installation of Secondary Vacuum System
Post 197 - Plenum Installation
Post 198 - Installation of Flywheel (Including Pilot Bearing), Clutch and Bell Housing
Post 199 - Removal and Installation of Harmonic Balancer/Front Cover
Post 200 - Compression Testing

ZR-1/LT5 Technical Calculations
Post 201 - ZR-1/LT5 Technical Calculations
Post 202 - Tech Info - LT5 Horsepower and Torque Calculations
Post 203 - Tech Info - ZR1 Differential Gearing and Vehicle Speed Calculations
Post 204 - Tech Info - ZR1 Wind Force, Rolling Resistance, Drivetrain Loss Calculations
Post 205 - Tech Info - LT5 Camshaft Timing Calculations
Post 206 - Tech Info - LT5 Pressure Drop In Oil Lines Calculations
Post 207 - Tech Info - RC SL4-205 injectors (500+ hp) Calculations
Post 208 - Tech Info - LT5 Summary of Camshaft Timing
Post 209 - Tech Info - LT5 Timing Diagrams
Post 210 - Tech Info - L98 Frisbee Horsepower
Post 211 - Tech Info - LT5 Coolant Flow Calculations
Post 212 - Calculating Alternator Pulley Diameter
Post 213 - Technical Calculations Reserved 1
Post 214 - Technical Calculations Reserved 2
Post 215 - Camshaft Compression of Lifter

Eliminated Systems and Added Systems
Post 216 - Eliminated Systems and Added Systems
Post 217 - Tech Info - Marc Haibeck on LT5 Eliminated Secondaries and Associated Anomalies
Post 218 - Tech Info - LT5 Added Systems
Post 219 - Elite Engineering Oil Catch Can Installation Details
Post 220 - Hans Meyer Check List with Additional Comments

LT5 Lifters, Camshafts, and Valves
Post 221 - Tech Info - LT5 New Rebuild Issues (Lifters, Camshafts, and Valves)
Post 222 - Lifters
Post 223 - Lifters and Valve Stem dimensions (reground valves)
Post 224 - Valve Stem Clearance Measurement Tool
Post 225 - Camshaft and Lifter Measurements (Stock and Regrind) all in inches
Post 226 - Valve Stem Clearance Measurements For Regrind Camshafts using Mellings JB 2236 Lifter
Post 227 - Regrind Camshafts Performance
Post 228 - Bad Z
Post 229 - Valve Stem Clearance Measurements For Stock Camshafts using Mellings JB 2236 Lifters

1995 (#0186) LT5 SPECIFIC TOP END REBUILD TRICKS
A 1995 Top End was rebuilt and best tricks linked here
Post 230 - 1995 (#0186) LT5 SPECIFIC TOP END REBUILD TRICKS
Post 231 - Clean Up of Valley, Installation of Battery Disconnect Switch and Coils
Post 232 - Installation of Rebuilt Starter, New Alternator, and Braided SS Oil Cooler Lines
Post 233 - Installation of Wilwood Rotors and C4 to C5-Z06 Conversion
Post 234 - Installation of New Secondary Port Vacuum System Lines
Post 235 - Installation of Reconditioned Injectors with New "O" Rings
Post 236 - New PCV Connections. Installation/Relocation of Plug Wires and New Spark Plugs
Post 237 - Blocking TB Coolant, Fluidyne Radiator and Thermostats
Post 238 - Reconditioning and Installation of Plenum with SS Allen Head Bolts
Post 239 - Addition of Billet Aluminum Power Steering, Water Pump Pulleys
Post 240 - New Rear Wheel Bearings and Half Shaft U-Joints
Post 241 - Rebuilt Black Label Transmission Installed and New Driveshaft U-Joints
Post 242 - Installation of Elite Oil Catch Can
Post 243 - Replacing the Coils
Post 244 - INJ1 Fuse Keeps Blowing
Post 245 - Under the Plenum
Post 246 - The Four Minute Plenum Installation
Post 247 - 1995 ZR-1 #186 with Haibeck Chip
Post 248 - K40 Front and Rear Radar Detection System
Post 249 - Oil Pressure Regulating Valve Cover Plate
Post 250 - All Aluminum Alternator Pulley

Summaries
Post 251 - Thermostat and Thermostat Housing Discussion
Post 252 - Operational Engine Stand
Post 253 - Buy High.....Sell Low
Post 254 - Windshields
Post 255 - Reserved
Post 256 - Bilstein Shock Applications and Self Alignment
Post 257 - Wheels
Post 258 - Winter Storage
Post 259 - Typical ZR-1 Restorations
Post 260 - Summary of ZR1 Restorations including 95' Crate Engine

Standard Corvette (L98)
Post 261 - 90’ (#8550) Corvette (L98) Modifications
Post 262 - Oil Cooler Modifications
Post 263 - Timing Chain Cover/Water pump Interference
Post 264 - Air Pump Eliminated
Post 265 - Aluminum Finned Oil Pan including New Milodon 18307 Oil Pump Pickup
Post 266 - Rebuilding Chrome Alternator
Post 267 - SS Air Intake
Post 268 - Installation of C4 Beam Plates
Post 269 - Oil Pan Drain Plug and Differential Case Drain
Post 270 - Wilwood 6 Piston Brakes with 13" Rotors and Wheel Alignment

Specific Summaries
Post 271 - Modifications Summary 5 ZR-1s
Post 272 - Crate Engine
Post 273 - 95' Drive/Half Shaft U-Joints, Rear Wheel Bearings
Post 274 - Cooler Termostats, Thermostat Modifications and Engine RPM
Post 275 - The Best Belt Tensioner Pulley
Post 276 - Air Filter Installation
Post 277 - Reserved
Post 278 - 30K mile Lt5 Parts Value
Post 279 - ZR-1 Check List
Post 280 - What To Look For When Buying A ZR-1

Additional Technical Information
Post 281 - The Improved LT5 Fuel Pressure Regulator
Post 282 - Changing Out Improved Fuel Pressure Regulator (IFPR)
Post 283 - Phil's (Jagdpanzer) Fuel Pressure Regulator Solution
Post 284 - New Secondary Port Throttle Vacuum System
Post 285 - Alternators
Post 286 - Cooler Thermostats, Thermostat Modifications, Engine RPM, and Fans
Post 287 - Replacing the Serpentine Belt
Post 288 - Water Pump Cavitation
Post 289 - Ron Davis Radiator Installation
Post 290 - Cayenne Pepper Keeps Mice Away
Post 291 - Reserved
Post 292 - Locating Relays Above Drivers Side footwell
Post 293 - Bypassing Clutch Safety Switch
Post 294 - Camshaft Abnormal Wear
Post 295 - Reserved
Post 296 - Oil Changes
Post 297 - VIN Number
Post 298 - Amsoil 10W-40
Post 299 - Infl Rest Inside The Car
Post 300 - Acceleration
Post 301 - ZR-1 Fluids
Post 302 - Kudos
Post 303 - Reserved
Post 304 - Loctite 518
Post 305 - Loctite 518/A136 Discussion
Post 306 - Fuel Pumps Billet Aluminum Connection
Post 307 - Removal of Front Bumper Facia
Post 308 - Reserved
Post 309 - Reserved
Post 310 - Parts Estimated Value
Post 311 - CD Player Lens Cleaner
Post 312 - Reserved
Post 313 - Reserved
Post 314 - Reserved
Post 315 - VATS Keys
Post 316 - Double Dunn Heads

Last UPDATE of post 2 Feb, 2024

Dynomite

LT5/ZR-1 Fluids

HammerZR1 initiated this list of ZR1/LT5 Fluids and I added photos and additional information

ENGINE OIL (LT5) ................. TRANSMISSION OIL (ZF S6-40)..........DIFFERENTIAL OIL Limited slip

8.6 quarts (with filter change) .....4.4 pints - Castrol TWS 10W-60 ............3.2 pints - Mobil 1 - 75W-90 Gear Lube
Amsoil 10W-40 AMO Motor Oil
Bosch 3401 Filter
FRAM TG 3985 Filter
Mobile 1 M1-207 Filter
................... ..................



Amsoil 10w-40 Recommendation/Analysis

Amsoil 10w-40

For L98 engine use Mobile 1 Synthetic 10W-30 and a Mobile-1 M1-111 Oil Filter.

See Notes below regarding oil change intervals.

Amsoil SAE 10W-40
Castrol 10W-60

1. CAPACITIES
Engine (LT5), with filter change...............8.6 quarts
Cooling System (ZR1), Initial Fill.......18.0 quarts
Manual Transmission (ZF S6-40)........4.4 pints
Differential (ZR1)............................3.2 pints

2. Fill and Drain Plug TORQUES
Oil Pan Drain Plug (14 mm Box wrench).....38 ft-lbs (5/8-18 Thread).
Actually a bit less torque with a bit of Permatex on the washer/threads.
The Oil Drain Plug is a Helicoil insert which is installed to reduce wear and tear on an Aluminum Thread.
A 14 mm open end flex head Ratchet works perfectly on Oil Drain Plug.



3. Manual Transmission Allen Plugs use 17 mm Allen Wrench (see Note D Below).
Fill Plug Allen wrench torque........26 ft-lbs
Drain Plug Allen wrench torque.....26 ft-lbs
Actually a bit less torque with a bit of Permatex on the washer/threads.

4. Differential Fill Plug use 3/8 inch Allen Wrench.
Always use a Fluid Pump when adding fluid to the Differential or Transmission.
Differential Fluid Change Intervals


5. Adding the Differential Oil Drain Plug to the ZR1 differential is a great idea.
The original ZR1 differential has no drain plug and the only way to remove differential fluid is to suck said fluid from the differential Allen Head Fill Plug. See Item #4 LT5 Added Systems

Install item # 584029 DIFFERENTIAL DRAIN PLUG KIT can be obtained from Corvette Central (includes 1/8 inch pipe tap, 11/32 drill bit) Differential Drain Plug Kit

Use 1/8 inch Aluminum allen head pipe plug you have to purchase separately 1/8 inch allen head pipe plugs

The kit provides a template that puts the hole just left of the center bolt in the valley of the differential. Just drill the hole gently and the differential oil and any shavings will drain completely. Then tap and install 1/8 inch Aluminum allen head pipe plug with a bit of Permatex on the threads. Do not tap too deeply to make sure the pipe plug is tight and flush when finished.

Flush a bit with Mobile 1 75/90 gear lube after completing the tap before installing the 1/8 inch allen head pipe plug.

6. RADIATOR COOLANT
You want to only use the green coolant. They have it at Napa and it meets 1825M GM Spec.

For Zerex the first gallon is called Regular Green Coolant (GM 1825M), the second gallon is called Original Formula (GM 1825M). Zerex ZXRU1 is 50-50 and Zerex ZX001 is undiluted. The third gallon is NAPA coolant (GM 1825M).

OROR



7. OIL FILTER
I concur with HammerZR1 on all fluids cited above except I am using the Mobile 1 M1-207 oil filter.
Mobile 1 M1-207 Oil Filter

8. BRAKE and CLUTCH FLUID
For brake and clutch fluid Dot 3 or Dot 4 (Prefer Dot 4).

Notes:
A. I change engine oil every 2,000 - 3,000 miles (5,000 miles if cross country driving).
B. ZF Doc says until someone invents a copper magnet, change the ZF S6-40 6-speed transmission oil at 10,000 - 12,000 mile intervals so as to minimize the amount of deposits of the suspended spent synchronizer material from collecting in critical component contact surface areas.
C. On previously owned cars/trucks, I change engine, transmission, differential fluid and coolant immediately upon purchase (extracting old brake/clutch fluid and cleaning brake/clutch fluid reservoirs). This assures proper fluid levels and reduces comtaminants accumulated over the previous life of the vehicle.

D. Be careful on inserting the 17 mm Allen Wrench into the Transmission Drain Plug. That Transmission Drain Plug often has road rash which prevents complete insertion of the 17 mm Allen. If not completely inserted you may strip the Allen part of the Drain Plug.
Snap-On 17mm Allen/3/8 socket

Dress up the Allen part of the Drain Plug and then tap the 17 mm Allen into the plug using a small hammer for full insertion before applying a torque on the 17 mm Allen Wrench to remove the Drain Plug. I use a box wrench that fits over the long end of the 17 mm Allen Wrench for additional leverage making sure you keep the 17 mm Allen Wrench fully inserted in the Drain Plug you are removing.

17 mm Allen Wrench


E. Oil Viscosity.

Newer engines are built with tighter tolerances (use lighter oil).
High Mileage engines lose tolerances (use heavier oil).
Hot climates (hotter engines) thin oil (use heavier oil).
Cold climates (colder engines) thicken oil (use lighter oil).
Often starting colder engines (lighter oil).
Running engines for long hauls once started (use heavier oils).
Newer synthetic oils do not loose viscosity with use (use lighter oils).
In Fl or CA coastal (use heavier oils).
In SD winter ....definitley (use thinner oils).
Frequent oil changes (use thinner oils).
Infrequent oil changes (use heavier oils).

F. Changing Engine Oil on the LT5.
Let the engine sit over night so you can remove the oil filter without a mess as Mike suggests. Yes...some oil filters have a check valve of sorts but on Mobile 1 M1-207s the filter can be removed without any oil mess after sitting over night.

The LT5 engine and oil cooler will hold about 12 quarts of oil of which you drain about 8-9 quarts on an oil change.
So you get about 70 % of the old oil changed on an oil change. Next time you will get 70% of that 30% old old oil (9% of old old oil remaing), and on the third change you will get 70% of the 9% old old old oil remaining with 3% of old old old oil remaining. And so it goes

The oil pick up screen in the LT5 Oil Pan sits about 1/4 inch from the bottom of the pan (has nothing to do with changing oil :p). When you drain oil (depending on how the ZR1 is sitting) you will have about 1/4 inch of oil in the bottom of the oil pan that does not drain.

On a ZR1 just purchased I will change oil twice within a week or so of each change to get down to the 9% of original "unknown" oil remaining.

Last UPDATE of post 3 Sep, 2022

Dynomite

General Bolt Length, Bolt Torque, Loctite, and Tools

1. In General bolt correct length checks can be determined by inserting the bolt (without turning) to the threaded portion of the receiver. For an 8 mm bolt, you should have approximately 7/16 to 1/2 inch of bolt showing (11 to 12.7 mm or 13 to 16 threads on a 1.25 t/mm bolt).

2. General Maximum Bolt Torque for steel bolts in aluminum if bolt torque is not specified.
Always use the correct size Drive Torque Wrench (1/4" Drive, 3/8" Drive, 1/2" Drive).
89 in-lbs on 6 mm bolts
19 ft-lbs on 8 mm bolts
30 ft-lbs on 10 mm bolts
40 ft-lbs on 12 mm bolts

LT5 Bolt Charts with suggested bolt torque, loctite and antiseize application information are included above. The free chart from Jerry's Gaskets which provided the basic LT5 component bolt sizes has been considerably modified into two charts above. The charts have been organized by function.




3. Loctite.
Red loctite 262 on all bolts except oil pan bolts, plenum bolts or anything you think you might remove a couple times. Use Blue loctite 242 on those items (Except SS Plenum and SS Cam Cover Bolts). Use Loctite 565 on sensors, switches, fittings. Use anti-zieze on plugs and injector housing coolant pipe bolts (on any stainless steel bolts) :mrgreen:

Nothing on new head bolts. Actually I use antisieze on Header Bolts with Stage 8 Header Bolt Locks.
Always use Stage 8 Exhaust Header Bolts with locks (Headers Only). Do not have to torque the Header Bolts too much as the locks will assure the bolts do not loosen (torqued header bolts into aluminum which area gets very hot makes removal of bolts at any time difficult). You can also use an Allen wrench on Stage 8 Bolts.

Use a bit of antiseize on Header Bolts with the Stage 8 Locks. Also use a bit of antiseize on all spark plugs.



4. Hydraulic Fitting Size comparison.
AN (Army and Navy).....-2.........-3...........-4.........-5.........-6..........-8........-10.......-12
Tube OD (Hose ID).......1/8".......3/16"...... 1/4".......5/16".....3/8".......1/2"......5/8"......3/4"
SAE thread size...........5/16-24..3/8-24.....7/16-20..1/2-20...9/16-18..3/4-16...7/8-14..1-1/16-12
Pipe thread size (NPT)..............1/8-27.....1/4-18................3/8-18....1/2-14..............3/4-14
Straight Metric
Thread Fine .....Male Thread....... Male Thread ......Female Thread..... Female Thread
....................... O.D. mm ............O.D. inches ........I.D. mm............... I.D. inches
M12x1.5 ...........12.0................... 0.47................... 10.5 ......................0.41
M14x1.5........... 14.0................... 0.55 ...................12.5 ......................0.49
M16x1.5 ...........16.0 ...................0.63................... 14.50 ....................0.57
M18x1.5 ...........18.0................... 0.71................... 16.5 ......................0.65
M20x1.5 ...........20.0................... 0.78 ...................18.5 ......................0.73
M22x1.5 ...........22.0 ...................0.87................... 20.5 ......................0.81

5. Aluminum Stat-O-Seal washers with molded Buna-N inner seals are much more reliable than the more common steel stat-o-seals. If the rubber portion fails to make contact all around the port, the aluminum will act as a crush washer, providing a reliable metal to metal seal. Use them to seal screws, bolts or plumbing fittings. The Buna-N seal is resistant to petroleum fuels and oils. Pegasus Auto Racing



Stat-O-Seal Inside Diameters vs. Outside Diameters
ID Size...#6 (0.138")..#10 (3/16")...1/4"..5/16"...3/8"..7/16"..1/2"..9/16"..5/8"...3/4"...7/8"..1.00"
OD Size............ .38".......... .44".. .50".. .60"... .66".. .76"... .88"...1.06"..1.19".1.32"..1.51".1.76" [/FONT]

6. Pipe Plugs.
1/8 inch NPT Drill is 21/64 or 11/32 inch. Aluminum Allen Head 1/8 inch pipe plugs found here. Speedway Motors

7. Tools.
Often a 1/4 inch socket wrench and associated extensions/swivels are better to use in tight places than 3/8 inch sockets. I use a 3/8 inch and 1/4 inch universal (the "U" joint) in the first picture. I have a complete set of metric and SAE sockets in 3/8 inch and 1/4 inch sizes.

The wobble extensions are in second and third pictures and flex ratchet combination wrenches in fourth picture.

You will notice what allows the wobble in the third picture.

There are all sorts of swivels and swivel socket combinations you can get but these four tools/tool sets will get er done assuming you have a good 3/8 inch and 1/4 inch socket wrench and set of metric sockets with 3/8 inch and 1/4 inch adapters.

Oh...ya...you might need a good 1/4 inch and 3/8 inch torque wrench also. I like the ones that trip at your torque setting. And.....a good set of allen and torx T wrenches.
.


8. New Tools These from Harbour Freight......

a. 1/4 inch drive Torx #40 hardened steel for Plenum and Cam Cover Bolts (just long enough to reach between those two tight runners on the Plenum).

b. 14 inch long combination 1/4 inch and 3/8 inch drive Flex Head Socket wrench strong enough (even using the 1/4 inch end) to remove the hardest to remove Torx Cam Cover Bolts. The 14 inch leverage eliminates the need for a cheater bar on the typical socket wrench.



Last UPDATE of post 4 Nov, 2022

Dynomite

Use of thread Lubricants, Loctite and Sealants

1. General Use of Loctite including Permatex.

In General use Red loctite 262 on all bolts except oil pan bolts, plenum bolts or anything you think you might remove a couple times. Use Blue loctite 242 on those items (Except SS Plenum and SS Cam Cover Bolts). Use Permabond A136 or Loctite 518 on Cam Covers. Use Loctite 565 on sensors, switches, fittings. Use anti-zieze on Spark Plugs a d Exhaust Manifold Bolts with Locking Tabs.

a. Permabond A136 or Loctite 518.
Use Permabond A136 very thin coat on surface of cam covers. Do not coat Permabond A136 all the way to the edge of the journals (stay away 1/4 inch). Coat the grooves with Permabond A136 for the two camshaft rubber plugs on each end of each Cam Covers.



b. Permatex on gaskets associated with Oil and Coolant.
There are several opinions on this but I use a very light coat of Permatex 300 Form A Gasket on both surfaces of mating parts of all assemblies in contact with oil or water (water pump, oil pan and oil filter housing assemblies). I always use a thin coat of Permatex on the Oil Pan Drain Plug, Transmission Fill and Drain Plugs and Differential Drain Plug also. This not only helps seal the plugs but also acts as a thread locker (A little less bolt torque with a good sealant). Tighten just tight enough to not leak on all drain plugs.



2. Use of Anti-Sieze and Gasket Sealants

I will use anti-sieze on stainless steel bolts, spark plugs, and header bolts (Permatex Anti-Sieze 133A). On the transmission (differential and engine) fill & drain plugs and water pump I use Permatex 300 Form-A-Gasket. On Cam Covers and Cam Cover rubber end seals use a thin coat of Permabond A136.



3. Bolt Torque Theory

When a sufficient load is applied to a metal or other structural material, it will cause the material to change shape. This change in shape is called deformation. A temporary shape change that is self-reversing after the force is removed, so that the object returns to its original shape, is called elastic deformation. In other words, elastic deformation is a change in shape of a material at low stress that is recoverable after the stress is removed. This type of deformation involves stretching of the bonds, but the atoms do not slip past each other. This applies to head bolts.

When the stress is sufficient to permanently deform the metal, it is called plastic deformation. This applies to camshaft sprocket bolts.

Now having said that.....what is the relationship between bolt torque, thread lubrication, and bolt tension?

The preload on a bolt, when determined via the torque method, can be off by as much as 25% even with proper precautions being taken especially between lubricated and dry bolt threads.

The purpose of bolt thread lubrication is to ensure that the applied torque deforms the bolt along its axis (stretch) instead of around its diameter (twist).

I have seen a statement that the standard for thread lubrication is a light coat of oil of about 10W viscosity. A thin coat of most engine oils does just fine. The idea is to allow the threads to move against one another and light oil does that reliably. Of course, this standard assumes that the threads of the bolt and nut, or case, or whatever, have reasonably smooth finishes. Exotic or extreme-pressure lubricants such as gear oils or moly pastes are mostly a waste of time and can actually be harmful if they reduce friction too much.

I on the other hand for oil pan bolts and other bolts on engine components such as the water pump, front engine cover (especially threaded into aluminum) use blue thread locker which by itself is a bolt lubricant. I clean and dry the bolt hole and bolt threads (I use a fine wire wheel on bolt threads including head bolts) with gasoline on a que tip for example cleaning out debree and oil films as much as possible. This applies to head bolt threaded holes as well.

You can reuse head bolts but I prefer to use new head bolts since I have no clue how they were first installed. It also depends on how hard they were to remove.

4. The use of Stainless Steel Bolts

There are only a few of us that use stainless bolts (and then only on cam covers and plenum). On the plenum if they are stainless bolts, I expect to be taking that off more often than not anyway. Prolly same with cam covers stainless bolts but less often.

On Cam Covers and Injector Housing Coolant Manifolds when SS Bolts are used I now use no loctite and no Antisieze using the Aluminum Stat-O-Seal washers. The Stat-O-Seal Aluminum washers with molded Buna-N inner seals are much more reliable than the more common steel stat-o-seals. The Stat-O-Seal Aluminum Washers act as a bolt sealing and locking mechanism. I use no Loctite or Antiseize on the Plenum SS bolts as the Plenum may be removed from time to time.

5. Use of Stat-O-Seal Washers

Using Aluminum Stat-O-Seal Washers..........if the rubber portion fails to make contact all around the port, the aluminum will act as a crush washer, providing a reliable metal to metal seal. Use them to seal screws, bolts or plumbing fittings. The Buna-N seal is resistant to petroleum fuels and oils. Pegasus Auto Racing



6. Thread Galling and Corrosion

Thread galling seems to be the most prevalent with fasteners made of stainless steel, aluminum, titanium, and other alloys which self-generate an oxide surface film for corrosion protection. During fastener tightening (and loosening), as pressure builds between the contacting and sliding thread surfaces, protective oxides are broken, possibly wiped off, and interface metal high points shear or lock together. This cumulative clogging-shearing-locking action causes increasing adhesion. In the extreme, galling leads to seizing - the actual freezing together of the threads".

The basic corrosion resistance of stainless steel occurs because of its ability to form a protective coating on the metal surface. This coating is a "passive" film which resists further "oxidation" or rusting. The formation of this film is instantaneous in an oxidizing atmosphere such as air, water, or other fluids that contain oxygen. Unlike aluminum or silver this passive film is invisible in stainless steel. It's created when oxygen combines with the chrome in the stainless to form chrome oxide which is more commonly called "ceramic".

7. Summary of 262, 242 Loctite, and Permabond A136.

Red loctite 262 on all (non stainless steel) bolts except oil pan bolts, plenum bolts, water pump bolts or anything you think you might remove a couple times. Blue loctite 242 on those items (Except SS Plenum and SS Cam Cover Bolts). Loctite 565 on sensors, switches, fittings.

LOCTITE 262 is designed for the permanent locking and sealing of threaded fasteners. The product cures when confined in the absence of air between close fitting metal surfaces and prevents loosening and leakage from shock and vibration. Typical applications include the locking and sealing of large bolts and studs (up to M25 ). The thixotropic nature of LOCTITE 262 reduces the migration of liquid product after application to the substrate.

LOCTITE 242 is designed for the locking and sealing ofthreaded fasteners which require normal disassembly with standard hand tools. The product cures when confined in the absence of air between close fitting metal surfaces and prevents loosening and leakage from shock and vibration. Suitable for applications on less active substrates such as plated surfaces, where disassembly with hand tools is required for servicing.

LOCTITE 565 is designed for the locking and sealing of metal pipes and fittings. The product cures when confined in the absence of air between close fitting metal surfaces and prevents loosening and leakage from shock and vibration.

Permabond A136 is designed for the Cam Covers and Cam Cover rubber plugs on each end. Permabond A136 from Jerry's



Last UPDATE of post 5 Aug, 2017

Dynomite

Service Manual Supplement, Secondary Diagnostics, Sensors and Prom Codes

1. Service Manual Supplement.
This Service Manual Supplement is limited to detail LT5 engine pictures, bolt torque, Sealant recommendation, and sequence of disassembly and assembly engine only. No electrical, diagnostics or fault finding (60 pages). Also included is Oil capacity, Engine Specifications, and Special Tools.



2. Checking Injector Resistance without removing Plenum.
I checked my primary injector resistances without removing Plenum. I disconnected my battery and connected Inj-1 fuse side toward front of my 1991 ZR1 through digital ohm meter to ECM connector A (drivers side most left connector) A8, A3, A2, A7, A1, A12, A13, and A18. I was looking for 12.5 to 14 ohms on primary and secondary injectors.



3. Checking Secondary Operation without removing Plenum.
Check Secondary Operation by grounding pin C17 of ECM with key on. My screw driver is now pointing at the location of pin C17 on the ECM (that wire is pink with black strip on my 1991).



4. ZR1 Sensors.


5. ZR1 Electronic Automatic AC .

The AC parameters can be viewed by pressing and holding the UP and DOWN Fan Buttons untill a -00- appears.
Then press the UP button untill you get to an - 05 (Battery Charge) or a - 16 (Coolant Temperature). Then press center Fan Button to view the Battery Charge (see below) or Coolant Temperature (Deg C). On a Standard 1990 Corvette (L98) the Coolant Temperature is scan UP to - 12 then press center Fan Button.

a. Coolant Temperature.
Coolant Temperature - 16 indicating you are .............Coolant Temperature is 83 deg C or 181.4 deg F
at Coolant Temperature (Now Press Fan)


b. The Coolant Temperature Calculation Trick.
Deg Centigrade which you observe as 83 deg can be converted to F deg:
(83 x 9/5) +32 = 181.4 deg F

c. Battery Charge.
A bit more complicated for Battery Charge...................Air is OFF in this case
Battery Charge - 05 (Now Press Fan)..........................197 indicating 14.408 volts (see d. below)


Battery Charge - 05 (Now Press Fan)
at Battery Charge -105 indicating 13.742 volts (see B below)
Air is ON in this case



d. The Battery Charge Calculations Tricks
With AC OFF we see 197. The Calculation for a positive number is:
((197/255) x 7 volts) +9 volts = 14.408 volts (the constant is 255 for a positive observed number)

With AC ON we see -105. The Calculation for a negative number is:
(105/155) x 7 volts) +9 volts = 13.742 volts (the constant is 155 for a negative observed number)

6. Prom Code Chart.



Last UPDATE of post 6 Aug, 2017

Dynomite

$24......Shows a gasket but came without a gasket....Price was right
Stant 14068 Thermostat

Jerry has the Rubber gasket
Stant 14068 gasket

1. The 180 deg versus the 160 deg thermostat or no thermostat.

We are referring to coolant temperature at the coolant temperature sensor.....

Why not just remove thermostat? NO...NO...NO!!!!

I run 180 deg thermostats in ALL ZR-1s.

A. At a coolant temperature of say 190 deg a 160 deg thermostat is open....so is my 180 deg thermostat. So from that point on our coolant system flow rates are identical at the same rpm. And so is the cooling.
Also see Defective Stant Thermostats

B. Using a 160 deg thermostat in cooler weather drops the engine coolant temperature below the designed engine temperature with the 180 deg thermostat. The PVC (at the cooler engine temperatures) is working at less than optimum temperatures as well as your oil and fuel functioning at less than optimum temperatures.

C. I see no difference between a 160 deg F thermostat and a 180 deg thermostat (both with the same Full Open Head Loss) once the coolant temperature has reached 190 deg F? I know the 190 deg F will be reached slower with a 160 deg F Thermostat but that is the only difference in that you reach the same Coolant Temperature at different rates of temperature increase. Kind of like using light weight pulleys to save HP which HP is only realized on acceleration as the rotational velocity of the pulley changes. Nothing is gained in a constant velocity (constant speed) situation.

FANS Oh....almost forgot.....my fans come on a bit sooner controlled by Marc Haibeck chip to help with engine temperatures when idling at a traffic light on a hot day (On at 205 deg F and Off at 200 deg F). But again....my 180 deg thermostat and the 160 deg thermostat are both open in that condition

Unmodified Fan Operation:
Primary Fan On 221-226 deg F (depending on Model Year).
Secondary Fan On 230 -234 deg F (depending on Model Year).

Modified Fan Operation:
Haibeck Chip (Fans On 205 deg F and Off 200 deg F).

2. Thermostat Multiple Functions.

The LT5 thermostat sits in two cavities and is located on the outlet side of the radiator. On one end of the thermostat is the first valve [pressure relief) that expands and opens to excessive radiator pressure (but only relative pressure over and above that normal thermal expansion radiator pressure). That valve is in the first cavity which is exposed to coolant outlet flow. In the second cavity is the second thermostat valve (temperature relief) which controls coolant inlet flow depending on engine temperature.

GM found at high rpm and high coolant flow, excessive pressure in the radiator, due to it's restriction, would blow the rubber seals between the side tanks and the core. GM did not want to design a specific LT5 radiator, so the solution was the radiator bypass which opens when the pressure differential across the radiator reaches a certain level. This bypass valve is part of the thermostat and, when open, allows coolant to recirculate within the engine.

When the Stant Thermostat is Fully Open the bottom end of The Stant Thermostat has two slots equating to approximately .07 square inches opening which feeds coolant back to the engine before passing the radiator. Again, even though the coolant passing through the thermostat from the radiator is of a lower pressure than the coolant passing the bottom of the thermostat before passing through the radiator (Radiator Head Loss), the total opening area of those two slots (.07 square inches) is very small compared to the approximately .75 square inches of a fully open thermostat. The effect of those two slots theoretically is negligible on hindering Engine Coolant passing from the radiator when the Stant Thermostat is Fully Open.

[b]ZR1 provided this photo in the LT5 Coolant System Discussion




3. Lets simplify......the discussion of the 160 deg thermostat cooling better than the 180 deg thermostat.

A. Let us say we have identical radiators, identical rpm, steady state coolant temperature, and both fans on and we are cruising at same speed.
B. Lets say coolant temperature is 190 deg in both your Z and my Z given everything identical in item #1.
C. Your 160 deg thermostat is full open with same flow rate as fully open 180 deg thermostat.
D. My 180 deg thermostat is full open with same flow rate as fully open 160 deg thermostat.
E. In other words...we both have been driving our Zs for say at least 30 minutes and have reached a steady coolant state.

Now......lets say the day gets hotter. The coolant temperatures should rise the same in both your Z and my Z given EVERYTHING else is the same

If it gets REAL HOT......both our Zs coolant will reach 230 deg at the same time.

The maximum temperature reached (given it is over 190 deg) will be no different for you than me even though you have a 160 deg thermostat and I have a 180 deg thermostat.

I am saying that my thermostat just maintains a minimum temperature higher than yours.
I am also saying your thermostat does not maintain a lower higher temperature than mine. Once both thermostats are fully open, the coolant temperatures are controlled by everything else mentioned in item #1 and not the thermostats (yours or mine).

4. Fans and Radiators.

Once your fan is on (my fan which may be on at lower temperatures is on).......we have identical radiator cooling no matter how hot it gets outside. The exception is Replacing the Fans with Higher Flow Rate After Market Fans which would solve the ZR-1 Over Heating Issue in Traffic on a Hot Day as long as you keep the rpms above 2,000 rpm(see item #6 below).

Now if we change radiators.....you run stock radiator and I run Ron Davis....DIFFERENT STORY as I have greater dissipation of heat than you at all rpms (water pump speed dependent) and ZR-1 speeds (air flow dependent).

5. Engine RPM.

My experience in all ambient temperatures.

A. In sixth gear running 65 mph (less than 2,000 rpm) the Coolant always gets a bit over 200 deg F. On Hot days the coolant will get a bit over 213 deg F. The key is the Water Pump is not pushing enough flow through the fully open thermostat to cool the engine to a Temperature where the Thermostat takes over (180 deg F).

B. If I shift to 5th gear at 65 mph (more than 2,000 rpm) the coolant temperature drops to Thermostat control (180 deg F) on cool days and drops to near 200 deg F on Hot days.



My findings are simply that the stock water pump is a bit low on coolant flow rate at rpms under 2,000 rpm. As you can see there is a big jump in Coolant Pump Flow rate between 1,000 rpm and 2,000 rpm and it is in this area or engine RPM that the Coolant Flow Rate is not sufficient in HOT Climates when the ZR-1 is moving in 6th gear at 65 mph.

The overheating issue when idling at a stop sign on HOT days (100 deg +) is more related to Fan Air Flow.
Tests at 50 deg F ambient.
Going 65 mph in 6th (1500 rpm) coolant temperature 205 deg F.
Going 65 mph in 5th (2200 rpm) coolant temperature 192 deg F.
Idling at 750 rpm coolant temperature 204 deg F.
Engine rpm 2000 rpm (not moving) coolant temperature rose to 213 deg F.

So...….At 65 mph it is the coolant flow. At 0 mph (Not moving with rpm at 2,000) it is the air flow.

If I could get the air flow higher while in traffic the issue would then be the coolant flow again where keeping rpm above 2,000 rpm would solve the High coolant temperatures on hot days in traffic.
The Coolant Pump Flow at 800 rpm is 15 gpm. The Coolant Pump actually gets more efficient as the rpm increases from idle to 2,000 rpm.
As Per Marc Haibeck graph provided to the ZR-1 Net email list by Graham Behan about ten years ago, the Coolant Pump flow rate through the engine (not the radiator or thermostat) is:
15 gpm at 800 rpm
18 gpm at 1,000 rpm,
44 gpm at 2,000 rpm,
65 gpm at 3,000 rpm,
90 gpm at 4.000 rpm,
120 gpm at 5,000 rpm at which time cavitation is starting.

The Block Resistance at 100 gpm was 20 psi during these tests which varies as the flow rate of the pump increases. The pressure on the output of the pump during the test was 3 psi at 2000 rpm, ramping up to 25 psi at 5000 rpm. As cited above, the hoses, radiator and bypass valve were not connected as a system as per Marc Haibeck Testing.
The Dual Thermostat Bypass pressure is apparently 5 psi and block resistance at 100 gpm is approximately 20 psi. I am not sure what the radiator Head Loss is at various flow rates but definitely depends on the radiator type which was not part of these tests.
It would seem that the Coolant Pressure Relief Cap on top of the Coolant Reservoir in front of passenger side set at 15 psi would assure the radiator maximum pressure would be 15 psi plus the Bypass Pressure of 5 psi or 20 psi.

6. Summary .....See LT5 Cooling and Radiators TIPS

A. Fans turn on at 205 deg F and OFF at 200 deg F (Haibeck Chip)
B. I use 180 deg Thermostats.
C. Ron Davis, Dewitt, and Fluidyne multi core Aluminum Radiators.
D. To solve the Hot Coolant flow when stalled in traffic would require Fans with Greater Air Flow.

The Thermostat is fully open at all coolant temperatures over 180 deg F (no need to use cooler thermostat unless you want to run at temperatures below 180 deg F).

The Water Pump does not provide enough flow to cool the engine at rpms less than 2,000 rpm. This is not an issue at ambient environmental temperatures on cool days. This is a problem on HOT days. The Aluminum Multi Core Radiators DO provide better Heat Dissipation and offer cooler Coolant at ALL Temperatures for which the 180 deg F Thermostat Controls the Flow (above 185 deg F Coolant temperatures the Thermostat is fully open). The Cooling effects then being dependent on Water Pump Flow Rate and Air Flow Rate through the Radiator.

Having the Fans come on at 205 deg F DOES provide for COOLER Coolant in the radiator once sufficient coolant flow rate is provided above 2,000 rpm. Using Aluminum Multi Core Radiators ALSO provides for COOLER Coolant Temperatures in conjunction with the Air Flow provided by Fans and Vehicle Speed. The Heat Removal Rate from the Radiator is greater as the Air Flow Increases and as the Aluminum exposed to that Air Movement increases.

It DOES make a difference if you are moving at speed in conjunction with Fans PULLING Air Flow as the additional Air Pressure Up Front does add to the TOTAL AIR FLOW through the Radiator at any ambient environmental temperatures.

Using 180 deg Thermostats insures that the engine will not run cooler than that temperature since the Thermostat is in control and controls the Coolant flow rate through the engine at all Coolant Temperatures less than 180 deg F.

7. Modifying the Stant Thermostat.

There has been some suggestions to drill 1/8 inch holes in the thermostat flange to allow better cooling.
Just tested several 180 deg F Thermostats for opening temperatures and found the Stants 180 deg Thermostat will start opening at 175 deg F with complete opening at 185 deg F. Marc suggested at one time the older Stants will deteriorate (Decrease in FUll Open Area) by up to 15% as they age. A thermostat with over 50k miles generally opens 5 degrees later and opens about 85%.

The Stants tested would be fully open with a flow area of approximately .785 square inches at 185 deg F.

Thermostat opening at 175 deg F....................................Thermostat opening at 185 deg F (Full Open)



A 1/8 inch diameter hole in the flange will offer additional flow area of .0123 square inches. Which one such hole will increase the total flow area by .016 or 1.6% (three 1/8 inch diameter holes would increase the flow area by 4.7%). This thinking does not address the change in coefficient of Discharge of such small holes.

Now compared to the normal aging of the thermostat of 15% over several years of use one would be much better off installing a NEW Stant Thermostat gaining 15% flow area as compared to drilling three 1/8 inch holes in an older Stant Thermostat only gaining 4.7% flow area.

Given the LT5 runs Hotter idling at a stop sign than at 2,000 rpm as cited in Item #5 in the link above a much better focus regarding engine Heating would be engine RPM (which relates directly to pressure on the coolant flow through the Stant Thermostat) and not the Stant Thermostat (Old or New).

8. The Thermostat housing and Heater Hose Connections.

Heater Hose Connection on Thermostat Housing

See Item #2 Replacing the Heater Core and Heater Hose Connection




Some Thoughts regarding the Thermostat Housing:

A. It does not make any difference if you use a 160 deg thermostat or 180 deg thermostat....they both are fully open at 185 deg.
B. I makes no difference if you drill small 1/8" holes in the thermostat flange as the additional area is only 1.5% increase per hole.
C. The Heater Circuit is open at all times even on a cool engine after start as the heater will be the first to get warm coolant.
D. On a very cold day with the heater on and Interior Fans set at Ten, the Heater Core with significant coolant flow could cool the engine for a significant amount of time before the main temperature controlled end of the Thermostat on the radiator side opens. The engine coolant mixed with some air would still expand into the radiator and to the coolant over flow below the passenger headlight.
E. If you want to cool your engine below the temperature controlled thermostat on a cold day or cool your engine a bit more on a very hot day, run your Heater with Interior Fans set at Ten using Outside Air (not recirculate) with windows open. The additional Coolant Flow through the Heater could be as high as 14% of the total coolant flow with 3/8 inch ID Heater Hoses.
F. The bottom of the thermostat on engine side opens at differential pressure of 5psi when open 1/2 inch allowing coolant to bypass the radiator (Marc Haibeck Testing).
G. When the thermostat has not reached opening temperature (175 deg) the coolant recirculates through the bottom of the thermostat at a pressure of 5psi since the coolant flow through the radiator is blocked.
H. Always use original green coolant GM 1825M.

9. Filling with Coolant.

I fill with Coolant/Distilled Water. Then the BIG Secret......
A. I use a vice grips and close off the coolant to the Plastic Overflow under Passenger Headlight.
B. I fill Black Coolant Reservoir in front of passenger side window and when the bubbling stops.....Blow into/pressurize that Reservoir holding pressure for about 10 seconds. More bubbles will come from the top of the radiator hose. I refill with Distilled Water and Blow into/pressurize the Coolant System again. I repeat this maybe three times until no bubbles come back from the top of the Radiator. I then replace the Coolant Reservoir Cap and remove Vice Grips.....and fire up the LT5 keeping a hand on the Injector Housing Coolant Manifolds to assure they get warm within a minute. (That Happens with this method of Coolant Filling 100% of the time).

With this procedure you are pressurizing both sides of the radiator but with each pressurizing cycle more coolant is being pushed into the coolant system and more air is bubbling out from the top of the radiator.

See Item #7 Blocking TB Coolant, Fluidyne Radiator and Thermostats

Last UPDATE of post 7 April, 2024

Dynomite

LT5 Radiator and Initial Coolant Fill Tricks

1. Ron Davis Radiator w/o transmission cooling

Coolant temperature stays at a constant 185 deg (70 deg F ambient) with 180 deg thermostat.*
a. 1989-1996 C4 Type V8 All Part No. 1-16CV8996
b. Rated 800 Hp
c. Manual transmission

* Coolant Temperatures will climb a bit with AC on (100 deg F ambient).



d. For the Ron Davis radiator the fan shroud inside baffles have to be cut back 5/8 inch so there is not contact with the fins of the radiator. Use a small cut off grinder for that task.
e. I cut the tab on the passenger side of the fiberglass radiator housing (the single tab with larger bolt hole that interferes the most with the oil cooler hoses). The fiberglass radiator housing then slipped on easily without further modifications.
f. Use a Radiator Comb to straighten out any bent fins.
g. Replaced Ron Davis Radiator Nylon Drain Plug with new radiator drain Brass JIC fitting with cap.



2. When installing SAMCO hoses, set the clamps so the screws are excessable after everything else is installed.
a. The bottom hose clamp screw on the water pump facing down so it can be reached from underneath with a long flat head screw driver.
b. That lower clamp (water pump) has to also be positioned so the screw part does not interfere with the belt tensioner.
c. The top main hose clamp between water pump and thermostat housing (Top) clamp screw facing to rear of engine.
d. This allows you to use a 7 mm box wrench to tighten the hose clamp from above. Make sure this TOP main Water Pump Hose does not touch the Oil Cooler Lines between the Oil Cooler and Oil Filter Housing.
e. Installing SAMCO hoses is kind of tough. I always used bit of Permatex on the hose fittings and in this case coated the inside of the hose a bit with Permatex also which helped start the hose on the various fittings. Trouble is that using Permatex makes the slip on easy but also slip off easy under pressure. So...USE NOTHING ON SAMCO HOSE.
f. I also use a bit of permatex gasket sealer on all mating surfaces (including those with gaskets) having to do with coolant (water pump, thermostat housing, all coolant hoses, and injector housing water manifolds).......no coolant leaks.
g. Use ONLY the SAMCO Hose Clamps with rounded edges that DO NOT cut into the SAMCO Hose when tightened.
h. Install all hose clamps on SAMCO hose as close to the receiving coolant pipe hose clamp retaining ring as possible. The hose clamp retaining ring is the larger diameter ring on all receiving coolant pipes.



3. Filling with coolant Tricks
See (Filling With Coolant and the Air Locked Water Pump) for Detailed New Coolant Filling Trick.

See LT5 Air Locked Water Pump Simplified for the Simplified Discussion regarding The Air Locked Water Pump.

Note: Getting the Air Out of the Water Pump after Blocking TB Coolant.

A. Disconnect the Drivers side Injector Housing Coolant Manifold "L" from the Drivers side Injector Housing Coolant Manifold and rotate that "L" up connected to the Drivers side Coolant Crossover Pipe.



Attach a second "L" to the Injector Housing Coolant Manifold rotated up and fill that "L" with coolant. Blow into that "L" forcing coolant into the water pump through the Drivers side Injector Housing Coolant Manifold (Only blow in steps refilling the "L" with coolant each blow effort). You can see in the photo that by blowing coolant into the Drivers Side of the water pump air will be forced out to the top level of the impeller with only a small amount of air left on the passenger side of the water pump.



B. Refill the Drivers Side "L" temporarily connected to the Drivers Side Coolant Manifold with coolant and do that trick a couple times until the coolant flows out of the Drivers Side Crossover "L" that has been rotated up.

When you blow (force) coolant into Port A of the Water Pump (Blowing in steps) you replace the yellow area of Air with Water. The Air is forced out the top and down left side through Port B. (Only blow in steps refilling the "L" with coolant each blow effort).

Do NOT rely on the temperature gauge to tell you if the Water Pump is functioning. If the two Injector Housing Coolant Manifolds are NOT getting warm rather quickly (within 1 minute), your coolant is NOT flowing.

4. The Simplified Method........I fill with Coolant/Distilled Water. Then the BIG Secret......
A. I use a vice grips and close off the coolant to the Plastic Overflow under Passenger Headlight.
B. I fill Black Coolant Reservoir in front of passenger side window and when the bubbling stops.....Blow into/pressurize that Reservoir holding pressure for about 10 seconds. More bubbles will come from the top of the radiator hose. I refill with Distilled Water and Blow into/pressurize the Coolant System again. I repeat this maybe three times until no bubbles come back from the top of the Radiator. I then replace the Coolant Reservoir Cap and remove Vice Grips.....and fire up the LT5 keeping a hand on the Injector Housing Coolant Manifolds to assure they get warm within a minute. (That Happens with this method of Coolant Filling 100% of the time).

With this procedure you are pressurizing both sides of the radiator but with each pressurizing cycle more coolant is being pushed into the coolant system and more air is bubbling out from the top of the radiator.


5. Coolant Overflow Under Passenger Side Headlight.
When the engine is Hot I fill the Coolant Overflow reservoir to within an inch of the top. On a Hot Engine the coolant overflow is filled by the expanding hot coolant to its maximum fill. As the engine cools the coolant is then sucked back into the engine.

What happens after doing some coolant draining during Plenum Pull or thermostat installations, is the engine develops Air Pockets in the coolant system. As the engine warms up to Hot these Air Pockets are pushed out of the engine into the Coolant Overflow. Once the Air gets into the Coolant Overflow the air is caught at the top of the coolant never to return to the engine (Which is exactly the purpose of the Coolant Overflow).

All the Air caught within the engine is flushed out by the Water Pump as you rev the engine once the engine has reached optimum temperature. The Air ends up within the Top Side of the Radiator where that Air is pushed out of the radiator into the top of the Black Coolant Reservoir in front of the Passenger Side Windshield. From their the air is forced into the Coolant Overflow as the Hot Air and Hot Coolant expands during engine Warm Up to Engine Hot.

If after several cycles of Engine Operation the Coolant Overflow continues to loose Coolant, You Have a Coolant Leak in your System.

Last UPDATE of post 8 Aug, 2017

Dynomite

HVAC Temperature Display And Radiator Efficiency Test Runs


1. Using HVAC Display for Engine Coolant Temperature.
This post applies to both C4 (L98) and (LT5) engines.

ghlkal brought my attention to this great tip

Using the HVAC Display parameter #16 digital readout for continous Engine Coolant Temperature in deg C where deg F=((9/5)(deg C) +32) can be accomplished by pressing the two Fan Buttons.

Press both Fan Up and Fan Down together waiting 3 seconds to enter HVAC diagnostics. Then press Fan Up to parameter #16 and then press Auto (between the two Fan Buttons) to read the Engine Coolant Temperature in deg C which Engine Coolant Temperature will be a real time continous reading.

The Engine Coolant Temperature is exhibited in real time continuously untill you exit the HVAC diagnostics or select another parameter by pressing Fan Up or Fan Down (engine running or not and idling in neutral or driving down the road). I shoot for 94 deg C to 104 deg C (200 deg F to 220 deg F) on a hot 100 deg F day at highway speeds with AC set at 72 deg (using a 180 deg thermostat and Fans On 205 deg F Fans Off 200 deg F with Marc Haibeck Chip ).

You can now compare Engine Coolant Temperature gauge reading to Engine Coolant Temperature HVAC digital read out. You can compare as a check of the Engine Coolant temperature gauge and two separate Coolant Temperature Sensors located essentially in the same area of the engine (drivers side inside IH under Plenum).

The Temperature Sensor (two pin connector) that controls the cooling fans also provides the information for the HVAC digital readout. The Temperature Gauge is controled by the adjacent Temperature Sensor (button terminal).

Photo provided by Jerry of Jerry's Gaskets.



2. Effectiveness of LT5 Radiators/Cooling Fan Systems.

The Bottom Line Question for any discussion regarding Effectiveness of LT5 Radiators/Cooling Fan Systems is How do the Radiator/Fans Cool the LT5 Engine with AC On at 100 deg F Ambient Temperatures while idling in traffic.

Let us assume for simplicity that LT5 engine cooling is about the Radiator Air Flow and Radiator Coolant flow (as 5ABI VT and Goldcylon suggests). Lets further assume that the engine sensors, heat generation, spark advance, compression, load are identical between engines at a certain engine speed and ZR-1 speed in other words nothing to consider other than the air flow, coolant flow, and coolant temperature from the HVAC Display (AC ON and AC OFF).

I am going to do some testing to verify exactly how two ZR-1s here in CA (90' with stock radiator and 91' with Ron Davis radiator) behave at 100 deg ambient temperatures (stop and go and on freeway at various speeds). I will determine exactly what the coolant temperatures are at 60 mph and 2,000 engine rpm in 5th Gear (including the worst condition idling with ZR-1 not moving). The Conditions I have are a 180 deg F Thermostat and Fans ON at 205 deg F and OFF at 200 deg F running on 91 Octane Fuel (Marc Haibeck Chip).

I am thinking ALL radiators function well at ambient temperatures around 90 deg F and lower.....it is the 100 deg F ambient temperatures that are of issue.

Using HVAC Display for Engine Coolant Temperature
Water Pump, Coolant Temperatures, and Coolant
Coolant Characteristics (Mix, Pressure, Elevation)

A. Experiment Number 1
1990 Fans On 205 deg F Fans Off 200 deg F
Stock Radiator
100 deg F Ambient
at least 50% Coolant Mix

AC On 72 deg AC Fan 7
Cruise 60 mph 5th HVAC temp 220 deg F (after exceeding that temperature during the idle test)
(this was interesting because once the temperature came down to 204 deg F with AC Off the temperature did not rise above 205 deg F with AC On)
AC Off 60 mph 5th HVAC temp 204 deg F and dropping slowly
Fans are Controlling Coolant Temperatures when AC is Off

AC On 72 deg AC Fan 7
Idle (not moving) HVAC 235 deg F and climbing (idle for 5 minutes)
Coolant Temperature would keep climbing if I did not turn AC Off within a few minutes

AC Off
Idle (not moving) HVAC 230 deg F and dropping slowly
Coolant Temperature CAN BE CONTROLLED by Turning AC Off

B. Experiment Number 2
1990 Fans On 205 deg F Fans Off 200 deg F
Stock Radiator
90 deg F Ambient
at least 50% Coolant Mix

AC On 72 deg AC Fan 7
Cruise 60 mph 5th HVAC temp 205 deg F

AC On 72 deg AC Fan 7
Idle (not moving) HVAC 228 deg F (idle for 10 minutes)
Coolant Temperature is stable at 228 deg F with AC On with Ambient Temperature 90 deg F

In Summary From this experiment at 100 deg F and 90 deg F Ambient Temperatures the 1990 ZR-1 with stock radiator and Marc Haibeck Chip controlling the fans On at 205 deg F and Off at 200 deg F the following results were obtained.........

1. The Fan thermal switching control the Coolant Temperature (100 deg Ambient) when moving with AC Off (With AC On the Fans are always On).

2. At 100 deg Ambient Temperatures the 180 deg thermostat is not a player staying open under ALL conditions.

3. At 100 deg Ambient Temperatures the Coolant System FAILS when idling in traffic or at stop lights for over 5 minutes with AC On.

4. Excessive Coolant Temperature at Idle with AC On can easily be controlled by turning the AC Off.

5. It also was determined that if the Ambient Temperature dropped to 90 deg F the 1990 ZR-1 can idle in traffic at a stop indefinitely with AC On.

(For those not having the Marc Haibeck Chip the Fan Controlled Coolant Temperatures in this experiment would be 234 deg F).

C. Experiment Number 3
1990 ZR-1 #72 (40,000 miles).
50 deg F - 70 deg F outside Air Temperature.
Ron Davis Radiator.
Haibeck Chip (fans ON 205 deg F, OFF 200 deg F).
Stock Exhaust.
180 deg F Thermostat.
Green Antifreeze down to -10 deg F.

6th Gear
65 mph
1,500 rpm
207 deg F Engine Coolant Temperature

5th Gear
65 mph
2,200 rpm
190 deg F Engine Coolant Temperature

17 deg F cooler running 65 mph in 5th Gear rather than running 65 mph in 6th Gear.
Did the cycle several times with identical results. Coolant Temperatures moved from min to max and back in a minute or two after shifting Gears.

Idle at 850 rpm 203 deg F.

D. Experiment Number 4
1995 ZR-1 #186.
70 deg F outside Air Temperature.
Fluidyne Radiator.
Haibeck Chip (fans ON 205 deg F, OFF 200 deg F).
Stock Exhaust.
180 deg F Thermostat.
Green Antifreeze down to -10 deg F.

6th Gear
65 mph
1,500 rpm
207 deg F Engine Coolant Temperature

5th Gear
65 mph
2,200 rpm
190 deg F Engine Coolant Temperature

17 deg F cooler running 65 mph in 5th Gear rather than running 65 mph in 6th Gear.
Did the cycle several times with identical results. Coolant Temperatures moved from min to max and back in a minute or two after shifting Gears.

Idle at 850 rpm 203 deg F.

Notes:

1. The Water Pump Flow at 800 rpm is 15 gpm. The Water Pump actually gets more efficient as the rpm increases from idle to 2,000 rpm.
As Per Marc Haibeck graph provided to the ZR-1 Net email list by Graham Behan about ten years ago, the water pump flow rate is:
15 gpm at 800 rpm
18 gpm at 1,000 rpm,
44 gpm at 2,000 rpm,
65 gpm at 3,000 rpm,
90 gpm at 4,000 rpm,
120 gpm at 5,000 rpm at which time cavitation is starting.
2. The Dual Thermostat Bypass pressure is apparently 5 psi and block resistance at 100 gpm is approximately 20 psi. I am not sure what the radiator Head Loss is at various flow rates but definitely depends on the radiator type.
3. It would seem that the Coolant Pressure Relief Cap on top of the Coolant Reservoir in front of passenger side set at 15 psi would assure the radiator maximum pressure would be 15 psi plus the Bypass Pressure of 5 psi or 20 psi.

See Post 120 - Thermostats, Fans, Radiators and Coolant Filling

Last UPDATE of post 9 Aug, 2017

Dynomite

Water Pump, Coolant Temperatures, and Coolant

Just when you think you have covered all technical issues. When I say "Water" I am talking about an "engine coolant mix" of your choice (Regular Green Coolant (GM 1825M) or Original Formula (GM 1825M)).

1. Water Pump Failures

a. Failed gasket causing water leaks.
* Water leaks from water pump gasket down on power steering unit or harmonic balancer.
* Water can be found on floor beneath front of engine.

b. Failed water pump bearing.
* Water pump pulley looks crooked.
* Squeeling or other noise from water pump area with engine running.
* Water pump pulley is loose or play can be felt by hand.

c. Water pump impeller spins freely on water pump shaft.
* Engine temp increases considerably.



2. Installing a Water Pump

It is difficult to install a water pump incorrectly. This water pump had no leaks in gasket and was free spinning by hand immediately after installation as a check. The water pump impeller was firmly attached to the shaft when installed.

If you drop everything on the floor after all that taking account of where the bolts go. Not to worry....

With the water pump in position on the front engine face, just insert the bolt into the water pump housing to the threaded area on the front engine face. Make sure you have about 3/8 inch (or a bit more or less) showing between the bolt head and water pump surface.

As you remove the water pump bolts (during water pump removal) you can confirm that bolt head to water pump surface distance. Some of those "water pump" bolts hold the front cover as well as the water pump to the engine block

All bolts should be about the same in this regard (bolt head to water pump surface distance). If you have more or less space between bolt head and water pump surface as the bolt begins to thread, the bolt is in wrong place.



I think this was an aftermarket water pump and the Solution to such potential disasters is to buy a new AC Delco water pump.

I use a very thin coat of Permatex 300 Form A Gasket on each side of the Water Pump gasket and IH coolant manifold gaskets before installing. I use a drop of Blue Loctite 242 on all water pump bolts and torque all water pump bolts 18 ft-lbs. NO LEAKS



3. Coolant Temperatures

Just got back with my 90' L98 climbing Grapevine on I-5 in 110 deg temps. I counted no less than 20 cars/trucks stopped alongside the road with hoods up (you know what that means)

My temps got up to 225 deg F climbing to the top with Air on. With Air off the temps dropped a few degrees. Just as a point of reference I was using HVAC for digital readout.

The radiator in my L98 is stock but in my 91' Z I have a Ron Davis Radiator.

Did some testing yesturday (91' ZR1 with LT5) in stop and go traffic at 105 Deg F (or higher) ambient temperatures....With Air on I approach 110 deg C Coolant Temperatures and with air off back down to 105 deg C. I ended up turning engine off at long stop lights. Cruising 25 mph more or less ....Coolant Temperatures with Air On stayed 105 deg C or less and once on the road cruising at 50 mph Coolant temperatures stayed below 100 deg C. This is with Ron Davis Radiator and Stock Fans coming on at 205 and both off at 200 degs (Marcs Custom Chips work perfectly).

I used HVAC Display to check continous digital Coolant Temperatures.

I would suggest that we have reached the limits of the cooling system and in particular, the limit is air flow through the radiator and around the engine (Fans). I would suggest if one really wanted to solve this issue, install higher flow rate fans. But then again we are talking extremes in Ambient Temperatures (100 deg and above or maybe mid 90s and above).

Since I essentially have the same results running a 90' (L98) and a 91' (LT5) in HOT ambient Temperatures hill climbing as well as in Stop and Go Traffic.......I would suggest a limit in the coolant systems has been reached.

Reaching Limits in Engine Cooling systems was not Abnormal climbing the Grapevine in temps over 105 deg F as many of those cars/trucks parked alongside the road with hoods up were relatively NEW cars and trucks.

4. Marc Haibeck Discussion of Voltage Effects on Engine Cooling

I asked Marc some questions regarding Cooling Fans and Cooling Fans operations with some very interesting facts/Observations presented by Marc. Marc gave me permission to post that information here.....thank you Marc

"The same OE fan is used on all '90 to '94 Corvettes regardless of the engine type. They run at high speed all of the time.

'90 - '92 Primary on at 226 degs. F, off at 216. Secondary on at 234 degs. F, off at 225.
'93 - '95 Primary on at 222 degs. F, off at 212. Secondary on at 230 degs. F, off at 221.
'95 ZR-1 has three fan relays which is different than the earlier years. On the '95 both fans are turned on at half speed at 222 degs. Both fans go on at full speed at 230 degs.

Many other GM cars have the fans wired for high or low speed. The fans are single speed but the relays turn on both fans wired in series for low speed. Then each fan gets power at six volts. For high speed the relays connect direct 12 volts to each fan.

I recently observed that the alternator output plays a significant roll in ZR-1 fan cooling. A typical alternator sets the system voltage between 13.5 and 14.5 volts when the ambient temperature is at about 90 degs. F.

In my opinion the cars with the alternators at the higher end of the normal range at 14.5 volts run a few degrees cooler. With the AC on there is also little more air flow from the interior vents for better AC performance. If fan engine cooling is a problem, consider the system voltage as a factor."

From this I would say also Battery Condition is a factor on maintaining the higher voltage for optimum Radiator Cooling Fans operations.

5. Coolant Selection SUMMARY

You want to only use the green coolant. They have it at Napa and it meets 1825M GM Spec.

For Zerex the first gallon is called Regular Green Coolant (GM 1825M), the second gallon is called Original Formula (GM 1825M). Zerex ZXRU1 is 50-50 and Zerex ZX001 is undiluted. The third gallon is NAPA coolant (GM 1825M).

OROR

NAPA

5. What is a Failing Coolant System.

85 C (185 deg F) is about when your thermostat is fully open (180 deg thermostat). The 96 C is when your fans prolly come on and 93 C is when your fans prolly turn off (Marc Haibeck Chip). Marc typically has BOTH Fans turn ON at 205 deg F and OFF at 200 deg F.

Now so far your testing at cruising (Outside Air Temperature right around 80 deg F) is not too significant. It is the idling at a stop light for several minutes (Outside Air Temperature 100 deg F) that is the BIG TEST which is FAILED by ALL stock Radiators cooling the LT5 (Especially with AC ON).

This Ambient Air Condition (100 deg F) and operational Condition (idling at a stop light) challenges the Most Efficient Radiators (Ron Davis, Dewitt, and even Fluidyne).

When I say FAILED....I am talking Coolant Temperatures greater than 110 C to 112 C (230 deg F to 234 deg F). It is interesting that the 234 deg F is when both fans come on (Stock Engine).

I am suggesting that Coolant Temperature of 234 deg F is NOT failing when Outside Air Temperatures are 100 deg F and you are idling at a stop light for several minutes.

I am also suggesting that without Marc's chip and with a stock radiator the Coolant Temperatures WILL EXCEED 234 deg F (on a 100 deg F day with AC ON idling at a stop light) which I would say is a failing Coolant System.

Also keep in mind the LT5 operating at less than 2,000 rpm does NOT provide a sufficient coolant flow rate to cool the engine no matter the air flow through the radiator on a HOT day.

See Post 7 - Thermostats, Fans, Water Pump, and Radiators

See Post 120 - Thermostats, Fans, Radiators and Coolant Filling

Last UPDATE of post 10 Aug, 2017

Dynomite

Keep the LT5 Cool using a Stant 180 deg F Thermostat and Ron Davis Aluminum Radiator.

See Post 120 - Thermostats, Fans, Radiators and Coolant Filling

Also Clean/straighten all fins on Oil Cooler and AC Condenser

180 deg F Thermostat



Ron Davis 1-16CV8996 Aluminum Radiator for 1990/1991 ZR-1s

1989-1996 C4 Type V8 All Part No. 1-16CV8996

-Rated HP: 800*
-Manual transmission
-Core is thicker than factory unit, shroud must be trimmed.



LT5 Thermostats
LT5 Radiator and Initial Coolant Fill Tricks

To read Digital Coolant Temperatures.....

1. Push and hold up and down (each side of Fan Control button) until you get zeros in display on left.
2. Then push up button to right until you get to 16 in the display.
3. Then push center fan button to read digital coolant temperature in degrees C continually in the display until you hit the temperature button.
80 C is 176 F
85 C is 185 F
90 C is 194 F
95 C is 203 F
100 C is 212 F
105 C is 221 F
110 C is 230 F
115 C is 239 F
120 C is 248 F
125 C is 257 F
130 C is 266 F

Radiator Debris Screens

91' ZR1 (LT5), 90' ZR1 (LT5), and 90' Corvette (L98).

Use 1/8 inch steel pop rivets with washers back side of Air Deflector and on front of screen (approximately 5/16 inch mesh). Drill 1/8 inch holes in the rubberized air deflector. Use cable ties on top side of screen (cable ties not required on 90' Debris Screen installation).

91' ZR1 (LT5) Slot in Debris Screen Required for Air Deflector Brace.


90' Corvette (L98)


90' ZR1 (LT5)


In the 90' Debris Screen installation you will see a slot in the Air Deflector for the Tow Bar when needed (see item #2 and #3) Lifting and Towing the ZR-1

The 90' Debris Screen (unlike the 91' Debris Screen) does not require a slot for the Air Deflector Brace.

The 91' Air Deflector has also been modified with Tow Bar slot but not shown in above 91' Debris Screen installation.

Last UPDATE of post 11 Aug, 2017

Dynomite

Getting The Air Out of the Coolant System

Eliminating the TB and Plenum coolant flow paths leaves you with this coolant flow shown in the diagram. I would assume water pressure/flow out of each injector housing (equal flow) into the injector housing coolant manifolds would push most of the air out of those manifolds and into the radiator which has a return line to the pressurized coolant expansion tank on passenger side near firewall (which IS the high point in the system).



Getting the air out of the Coolant flow

It is assumed the air gets pushed out of the injector housing coolant manifolds on each side (equally) since they are higher than the radiator coolant line going back to the coolant expansion tank on passenger side (the highest point in the coolant system).

It appears that the water pump pressure and resulting coolant flow into each cylinder block (right and left) would be close to equal since the coolant flow is separated almost equally on the face of the front cover where the water pump is mounted. The exception here is the length of the coolant path from the water pump impeller is longer on Passenger side which could explain a bit higher coolant pressure on Drivers side to assist TB Coolant Flow from Drivers Side to passenger side. There are two holes of equal size that go into the front of each cylinder block (right and left) from the front cover. In other words, the coolant is not pushed from the water pump into a single flow after which the flow is divided but rather the coolant flow is divided at the impeller of the water pump.



If the water pump can pump 100 GPM (385 cubic inches/sec) through two ports (lets assume 1-1/4 inch diameter or 1.23 square inches cross section each port), the coolant velocity would be 156 in/sec or 13 ft/sec in each port. That is intuitively enough flow to prevent a bubble of air going the other way in that flow assuring all air is pushed out of the system.

The Water Pump Flow at 800 rpm is 15 gpm. The Water Pump actually gets more efficient as the rpm increases from idle to 2,000 rpm.
As Per Marc Haibeck graph provided to the ZR-1 Net email list by Graham Behan about ten years ago, the water pump flow rate is:
15 gpm at 800 rpm
18 gpm at 1,000 rpm,
44 gpm at 2,000 rpm,
65 gpm at 3,000 rpm,
90 gpm at 4,000 rpm,
120 gpm at 5,000 rpm at which time cavitation is starting.

It is assumed the water pump is NOT air locked which is the first thing to check for when refilling with coolant. See Filling With Coolant and the Air Locked Water Pump

A Simplified Method.......I fill with Coolant/Distilled Water. Then the BIG Secret......
A. I use a vice grips and close off the coolant to the Plastic Overflow under Passenger Headlight.
B. I fill Black Coolant Reservoir in front of passenger side window and when the bubbling stops.....Blow into/pressurize that Reservoir holding pressure for about 10 seconds. More bubbles will come from the top of the radiator hose. I refill with Distilled Water and Blow into/pressurize the Coolant System again. I repeat this maybe three times until no bubbles come back from the top of the Radiator. I then replace the Coolant Reservoir Cap and remove Vice Grips.....and fire up the LT5 keeping a hand on the Injector Housing Coolant Manifolds to assure they get warm within a minute. (That Happens with this method of Coolant Filling 100% of the time).

With this procedure you are pressurizing both sides of the radiator but with each pressurizing cycle more coolant is being pushed into the coolant system and more air is bubbling out from the top of the radiator.

Thermostat bypass

The radiator Bypass Hose (see above coolant flow diagram) contains the hot coolant coming from the passenger side injector housing as stated below in red. The other companion hose (Radiator Inlet Hose) coming from the drivers side injector housings goes to the top (return line) of the radiator.

Both hoses are connected together at the top front of engine so the coolant flow from each injector housing may comingle with either the radiator bypass or radiator inlet.



Coolant refilling........See LT5 Radiator and Initial Coolant Fill Tricks

Coolant Overflow Under Passenger Side Headlight.
When the engine is Hot I fill the Coolant Overflow reservoir to within an inch of the top. On a Hot Engine the coolant overflow is filled by the expanding hot coolant to its maximum fill. As the engine cools the coolant is then sucked back into the engine.

What happens after doing some coolant draining during Plenum Pull or thermostat installations, is the engine develops Air Pockets in the coolant system. As the engine warms up to Hot these Air Pockets are pushed out of the engine into the Coolant Overflow. Once the Air gets into the Coolant Overflow the air is caught at the top of the coolant never to return to the engine (Which is exactly the purpose of the Coolant Overflow).

All the Air caught within the engine is flushed out by the Water Pump as you rev the engine once the engine has reached optimum temperature. The Air ends up within the Top Side of the Radiator where that Air is pushed out of the radiator into the top of the Black Coolant Reservoir in front of the Passenger Side Windshield. From their the air is forced into the Coolant Overflow as the Hot Air and Hot Coolant expands during engine Warm Up to Engine Hot.

If after several cycles of Engine Operation the Coolant Overflow continues to loose Coolant, You Have a Coolant Leak in your System.

Last UPDATE of post 12 Aug, 2017

Dynomite

TB Coolant Discussion

Some guys who swear by the fact that TB coolant flow keeps the TB warm and prevents icing are missing some key technical issues me thinks

Explanation

1. The TB Coolant is not a flowing system once the engine is heated up. The TB coolant on passenger side connects to a "T" back to the pressurized overflow tank just in front of the passenger under the hood (highest point in the system). The "T" is in the line from the air vent/heat expansion path from the top passenger side of radiator. That radiator vent/heat expansion path is also NOT flowing once the engine heats up. The TB Coolant Design is in regard to VENTING Air and not TB heating and then only during initial engine heating up (And then only if you have a lot of air in your coolant system after opening up your coolant system for repairs or leaks such as coolant leak repair or Plenum/IH Housing, Head removal or Water Pump/Thermostat/Radiator repair).

2. The TB coolant and top side of radiator vent back to the pressurized expansion tank (High point in coolant system) receive air/coolant as the engine is heated up and coolant/air in the system expands.

3. As coolant/air expands (as engine is heated up) the excess air/coolant overflows through the pressurized radiator cap in that high point pressurized expansion tank to the coolant reservoir under the passenger side headlight.

4. The purpose of that system is to allow coolant/air to move back and forth between the coolant expansion tank and coolant reservoir as coolant/air expands during engine heats up/cools down purging the system of air. This occurs by the fact once the coolant system air is forced out the pressurized radiator cap to coolant reservoir, only coolant returns from the reservoir as the coolant system retracts while engine cools once turned off (assuming you have proper coolant levels in the overflow tank under the passenger side head light).

5. Now back to TB coolant.............There is no coolant/air flow between the top side of radiator or TB to the coolant expansion tank on passenger side (high point in system) once the engine is heated up. A CAVEAT would be the small coolant head loss in the IH manifolds to the top side of radiator which would be equalized by a identical small coolant head loss of any flow through the TB and back to the top side of radiator via the coolant expansion tank (a very small diameter line and a very small coolant flow rate).

6. It appears to me that the only reasons for TB coolant (when there is movement of coolant/air between top side of radiator, TB, and expansion tank) is:
A. To warm up the TB QUICKER during engine initial heat up and to move coolant/air from the IH housing coolant manifolds back the coolant expansion tank quicker. This all happens when you first start the engine up when the thermostat is closed and radiator circulation is stagnant.
B. To prevent icing of the Throttle Body when temperatures are below approximately 10 deg F.

7. In other words, with the LT5 coolant system at first start up with a cold engine the coolant is recirculated entirely in the engine and not through the radiator. The TB coolant as the engine coolant expands then allows coolant/air a path back to the coolant expansion tank when there is no return of that expansion from the radiator since the radiator is cold and not functioning yet.

8. Once the thermostat opens up the radiator coolant expansion occurs as the radiator heats up pushing more air from the top side of the radiator to the expansion tank. So if you block the TB coolant you do not let the air out during initial engine coolant heating but that is not an issue if you do in fact have most of the air out of the system during initial coolant fill. Coolant/air can expand through the radiator even though the thermostat is closed however as the engine heats up.

9. The coolant system air has a second chance to excape to the expansion tank during radiator coolant/air expansion once the thermostate opens up allowing hot coolant to flow through the radiator.

10. Throttle Body Coolant Line Blocked


A. You can Block TB Coolant at Injector Housing.
You can Block TB Coolant at Injector Housing without removing Injector Housings.
Recommend removing Two Injector Housing Coolant Manifolds to Block TB Coolant at Injector Housings.
You can then keep or eliminate the Plenum hoses/tube on passenger side or leave it in place.
No more hose clamps required on the TB Coolant Hoses to TB if you want to leave the stock look.
You do have to Block TB Coolant near Coolant Reservoir if you Block TB Coolant at Injector Housing.
B. You can also Bypass TB Coolant with the Coolant circulating through the Injector Housing/Plenum.

1991 LT5 with TB Coolant Blocked at Injector housing,
ALL TB Coolant Hoses and Tube eliminated using 1/8 inch Allen Pipe Plugs


1990 LT5 with TB Coolant Blocked at Injector housing, ALL TB Coolant Hoses
and Tube In Place


Last UPDATE of post 13 Aug, 2017

Dynomite

Coolant Characteristics (Mix, Pressure, Elevation)

High Coolant Temperatures have happened before........stay out of slow traffic in hot weather for long periods of time especially climbing steep hills.

Check for coolant in the oil (coolant will sit at the bottom of oil pan). Check for oil in the coolant (oil will float on top of the coolant in the coolant reservoir in front of passenger side). If your oil level seems to be increasing or decreasing or your coolant level decreasing abnormally that is another indicator. You are checking for a failed Head Gasket.

Do a compression test once in a while to make sure nothing is going on with head gasket, valves, rings.

Then sit back and drive up that hill keeping the speed up to at least 20 mph....40 mph preferred........you NEED some dynamic air flow around the radiator

If you continue to do this......definitley turn on your fans at lower coolant temperatures and Turn your AC off at those high temps when climbing that hill (better for you to suffer than your engine)

Stock Fan Control on ZR-1s
'90 - '92 Primary fan on at 226 degs. F, off at 216 degs. Secondary Fan on at 234 degs. F, off at 225 degs.

Marc's chips turn Cooling Fans on at 205 deg and off at 200 deg. Those Chips will give you a few minutes more of cooling you do not have with a stock chip maybe enough time to get you to the top of the hill

Custom Engine Calibrations
LT5 Performance Engine Calibrations

I expect you will have NO issues unless you have run with loss of coolant such that you were circulating air entrained coolant. Or coolant mix was such that those temperatures caused coolant to boil off which you would notice in your coolant overflow tank under right headlight

This from a Google Search for Specifics on Boiling Characteristics of Coolant
The pressure cap on a cooling system is the key to raising the boiling point of the 50/50 mix of antifreeze and distilled water. For every pound of pressure cap rating the boiling of point of the above mixture raises 3 degrees. If you had plain water in your cooling system with a 15 pound pressure cap the water would boil @ 257 degrees. If you had a 50/50 mix of antifreeze and water the coolant would boil @ 265 degrees with a 15 pound cap. The boiling point would raise to 270 degrees if you had a 60% antifreeze mixture with a 15 pound cap. If you had a 70% mixture the boiling point would raise to 276 degrees.

Don't be fooled by the old wives tail that by adding a richer antifreeze mixture will keep the complete system cooler. In fact it works just the opposite. As you know pure antifreeze has a higher viscosity rating than plain distilled water. The higher the antifreeze mixture percentage its ability to adsorb heat from the engine goes down. The higher the antifreeze mixture percentage also retards the radiator's ability to get rid of the coolant heat.

Race cars use pure water in their cooling systems because it adsorbs heat from the engine and gets rid if it in the radiator better than any antifreeze mixture.

It's to your cooling systems advantage to mix your pure antifreeze/water mixture to protect the engine from freezeing 10 degrees lower than last years coldest day last winter.

Pure antifreeze boils @ 387 degrees Farenheit in atmosphere.

I also happen to know you are at high elevations

This from a Google Search on Specifics on the Boiling Characteristics of Coolant Related to Elevation
With NO pressure cap......Water boils at 212 degrees at sea level. Water boils at 204 degrees at 4,000 feet elevation. Water boiled at 192 degres at 9,000 feet elevation. A 50/50 mixture of water to anti freeze will boil at 227 degrees at sea level. A 50/50 mixture of water to anti freeze will boil at 220 degrees at 4,000 feet elevation. A 50/50 mixture of water to anti freeze will boil at 212 degrees at 9,000 feet elevation. The anti freeze referred to here is ethylene glycol based. Both of these are with no pressure cap on the radiator. You can add 7 degrees to the boling point with the addition of each 1lb of pressure on the pressure cap.

Last UPDATE of post 14 Aug, 2017

Dynomite

Lifting The LT5

1. Engine Lift
a. Harbor Freight 2 Ton Engine Lift set on 1 Ton for this lift.
c. 1 Ton setting provided the reach to install the engine in the ZR-1 while on KwikLift with Hood installed.



2. TIPS and Notes Additional TIPS
a. ZR-1 on KwikLift with front lowered to assist in tilting engine to rear during installation.
b. Remove windshield wiper motor (drivers side). *
c. Engine was installed without the bell housing, plenum, fuel rails. **
d. Use custom design spreader bar under the load leveler and Harbor Freight 2 ton hydraulic lift. ***
e. With this setup, you can install LT5 in ZR1 on KwikLift with front of ZR1 facing forward (front of KwikLift on ground).
f. Leave hood on.
g. With this set up I have recently pulled an LT5 with SW Headers installed with no issues. You cannot use the standard lift eyes if you want to install the LT5 with headers however (use soft slings around Flywheel and Harmonic Balancer). See Installing Engine In ZR1

*Note: Reach through windshield wiper grille (the small removable access above windshield wiper motor arm connection). With socket wrench just loosen the two nuts on each windshield wiper arm (DO NOT REMOVE THOSE NUTS). Slide both windshield wiper arms off the motor sockets. Relube those windshield wiper sockets on the motor when reinstalling the windshield wiper arms. Remove the three bolts holding the windshield wiper motor in place and remove motor. Locate the wiper arm at 5:00 clock time looking toward front of engine. To reinstall the wiper arms reaching through the removable access with a long needle nose plyers you can slip the arms back on the socket and tighten the nuts after you reinstall the wiper motor. Relocate the wiper arm at its home postion before attaching the wiper arms (9:00 clock time looking toward front of engine). How to Replace the Wiper Motor

**Note: Install Cam Covers and plugs before installing the engine in the Z. This prevents anything from falling into the Camshaft area or Cylinders during engine installation. It is much easier to install Cam Covers with engine out of Z vice with engine installed (requires the loosening of "C" Beam Plates and Motor Mounts to tilt engine down in rear for access of two lower rear Drivers Side Cam Cover Bolts).

***Note: The custom design spread bar adapter was used to match the distance between the standard LT5 lift padeyes and Load Leveler lift points. The Load Leveler is attached to hydraulic lift on a swivel which allows the engine to be rotated around the vertical axis. You cannot use the standard lift eyes (shown in photo) if you want to install the LT5 with headers however (use soft slings around Flywheel and Harmonic Balancer).



3. Summary Installing a LT5 in a 91' ZR-1
a. I removed the Wiper Motor as Ben suggested which was a 15 minute job. That removed the possible contact of the Wiper Motor with my powder coated Cam Covers while lowering the Harmonic Balancer past the front cross member

b. I installed the LT5 without Plenum, or Bell Housing. Those items were attached after the engine was installed in the Z.

c. I used KwikLift ramps sloped down in front for engine installation and then raised for completion of component installation.

d. It was easy sliding (KwikLift Creeper) under the Z for Bell Housing installation followed by Transmission and Drive Line installation with "C" Frame alignment.

e. That followed by SW Headers and SW exhaust system installation and adjustment.

f. The Ron Davis Radiator was then installed last adjusting ALL SAMCO coolant hose clamps for accessability using my flat screw driver. The last SAMCO hose installed was the short "L" on the drivers side IH Housing Coolant Manifold after filling with coolant making sure I had coolant at that level.

g. Installing the Plenum after engine installed was almost a necessity as the starter electric and Ignition Module (attached under the Plenum) electric was accessable only within the engine compartment. This also was a necessity for installation of the AC Compressor (before installation of the Plenum) under the Plenum (AC not disconnected). The Power Steering Pump was then connected to its position in front of the drivers side Head without disconnecting Power Steering Hydraulics.

h. I installed the Wiper Motor and Plenum after the engine was installed avoiding contact of the MAP sensor with the rear firewall. Installing the Wiper Motor and Plenum was a 15 minute job for each with engine installed.

I wanted to get used to installing the Plenum with engine installed

The only thing I forgot to do before I installed the LT5 was check the Oil Pressure Regulating Valve (OPRV) Cover bolts for tightness which I later did but hard to accomplish with engine installed

Last UPDATE of post 15 Aug, 2017

Dynomite

Lifting and Towing the ZR-1

See ZR-1 Transmission Install and Lift Tricks for a general discussion related to lifting the ZR-1 during transmission installation.

1. Lifting the ZR-1.
ZR1 Lifting techniques using a floor jack, jack stands and ramps are described herein. A Steel adapter has been designed and proven safe to lift the rear axle directly under the center of the rear spring mount using a floor jack. The ZR1 can be lifted to a height such that ramps can be inserted from the side under each rear wheel.

A Wooden Drive On Adapter has also been designed to get the front lift point (The front cross member just in front of the oil pan) high enough so a Floor Jack can be positioned under the Front Cross Frame (one Wooden Drive On Adapter is used under each front wheel). The Front Wooden Drive On Adapter consists of three 2x12s (you can see the approximate lengths of each of the three pieces) screwed together to form a single Wooden Drive On Lift. The Wooden Drive On Adapter allows you to drive on without interferring with the front skirt.

The ZR1 can then be driven off the ramps when work is completed without any further use of a floor jack. The adapter can be positioned on a floor jack lift pad and rolled under the spare tire area directly under the rear spring mount just behind the stock exhaust system.

The adapter is a 4 inch OD by 3/8 wall extra strong pipe section 5 inches long.

The pipe adapter is captured between the rear spring mount bolts, exhaust, spare tire on the ZR1 and by the floor jack lift pad which is usually cupped securing the pipe adapter from lateral movement.

The Steel Pipe Adapter


Lifting the Rear Axle


The Drive Off Ramp under each rear wheel..................The Drive On Adapter under front wheels


Lifting The Front Cross Frame (note wood block between jack pad and cross frame)
When jacking the front center I use a 2x4x6 pad placed under the cross member so it is beneath the front part with the vertical stiffener. If you jack in the center of that cross member it will bend up a tad which you do not want to do.



Now it you jack up one side very high that does twist the body so I tend to limit the height I jack one side.
I just jack high enough at the side (just behind the front wheel) jacking points (not on the plastic but on the steel rim where it curves) to just getting the tire free of the ground for removal.

Front just behind front Wheel Well between two Hash Marks


Rear just in front of rear Wheel Well between two Hash Marks


The Best Jack is this 3 Ton Floor Jack from Harbor Frieght


2. Towing the ZR-1.

Emergency Kit.....15 ft tow rope (5,000 lb vehicle rating), Jumper Cables, Tow Adapter, Lug Wrench


Daniel_Mc provided a concept/photo of a Tow Adapter for a ZR-1 that in its simplicity I just could not pass up
So......I designed one after the photo provided by Daniel_Mc and had a local steel shop fabricate the Tow Adapter.
I did some towing tests to see if there are any issues or limitations. One limitation will be towing at an angle in a turn which this adapter without being bolted on the back side of the cross member will not function (that did not seem to be an issue during the tow tests). The Tow Adapter is made from 1/8 inch steel plate which is substantial and flexible enough to tow the ZR-1 with Nylon Tow Ropes having a steel hook on one end.



The Tow Adapter is made to engage the 1-1/4 inch square tubing of the frame support under the front of the ZR-1.


A. Tow Adapter Description.

When needed for towing, the Tow Adapter is slipped through a 4 inch x 1/8 inch slot in the front Air Spoiler. There are two 1/2 inch holes (not shown in photos) in the Tow Adapter plate (one for 90' and one for 91') depending on which model year you use the Tow Adapter. 1/4 inch Allen Head Bolts are inserted into one hole or other with large Pan Head Washers on each side (and adjusted snug against the Air Spoiler. The 1/4 inch Allen Head bolt keeps the Tow Adapter in place if you want to keep it installed as you drive.


The best tool to make the 4 inch x 1/8 inch slot in the front Air Spoiler is an Angle Grinder (with Cut Off wheel).
The Tow Adapter sticks out beyond the skirt about 4 inches on a 91' and about 6 inches on a 90'.



A nylon tow rope (a steel hook on the end is required) can be attached to the receiver in the Tow Adapter (2 inch x 2-1/2 inch hole).

B. Installing the Tow Adapter.

The Tow Adapter is simply installed by reaching under the Air Spoiler and inserting the front tip of the Tow Adapter into the slot in the Air Spoiler. Push forward and then lightly tap the rear of the Tow Adapter onto the cross member with a small hammer. The Tow Adapter is removed by lightly tapping on the front tip of the Tow Adapter with a small hammer.

C. Testing Tow Adapter.

The Tow Adapter was tested towing the 91' ZR-1 with a lawn tractor on gravel. A small nylon sling was used for towing. The Tow Adapter was NOT bolted to the frame in any way.



When towing at an angle of 45 degrees the front wheels were turned in the direction of towing. With a lawn tractor and the use of this Tow Adapter, the ZR-1 could be backed into the street and with a lawn tractor pulled and then releasing the clutch in second gear starting the engine if your battery is dead. There was no deformation of the Tow Adapter during these tests

Towing in a straight line......................................... ...Towing at an angle of 45 degrees.


D. Storing Tow Adapter.

I have elected to carry the tow adapter on the right side of the passenger seat where it fits perfectly with my Gorilla Lug Wrench. I have found with the tow adapter installed it is easy to hit it with a curb when parking. It is very easy to slip in place if needed without jacking the vehicle.

Tow Adapter Stored next to Passenger Seat......................Gorilla Lug Wrench



Last UPDATE of post 16 Mar, 2018

rickyrj1

Tremendous post! Great Job & Thank You for your time & effort in putting it together.

Dynomite

The Oil Filter Adapter has many important functions. The Oil Filter Adapter is NOT for the sole purpose of holding/adapting the Oil Filter.

The oil paths through the Oil Filter Adapter Housing are describe in Item #5 below.

1. A Discussion of the Functions of the Oil Filter Adapter.
a. Control Oil Temperature. See Related ECM Code #52 Item #3 ZR1 ECM CODES 1990 TO 1992
b. Provide Sensor Feedback to the Instrument Panel.
c. Provide Oil Filtration.
d. Assure proper Oil Flow at any Oil Temperature.
e. Assure proper Oil Flow with contaminated Oil Filters.

The Oil Pressure Regulating Valve situated between the Oil Pump and Oil Filter Adapter controls and maintains Consistent Oil Pressure.

As an aside
2. Oil Pressure Sensor (Dash Gauge) Malfunction I changed out the oil pressure sensor for the dash gauge (top of oil filter) after engine installation. Oil pressure cold was registering 75 lbs. After changing out the oil pressure sensor, oil pressure is registering 55 lbs steady hot or cold and does not increase much with revs.

Oil Filter Adapter Sensors ........................................ ......Oil Filter Adapter Ports and Sensors


3. LT5 Oil Pressure and Oil Temperature Regulation

a. The Oil Pressure Regulation Valve (OPRV) (just after oil pump) opening pressure is 50-60 psi.



b. The Oil Cooler Bypass Valve on the Oil Filter Adapter allows oil to bypass the open oil cooler at hot temperatures since oil cooler is a bit restrictive. This valve raises the pressure a bit on the flow trying to bypass the oil cooler making sure some oil does go through the oil cooler.
c. The Oil Temperature Control Valve on oil filter housing opens oil flow from the oil cooler. The temperature opening characteristics of this valve are Thermostat-Open-203 degree F, Fully open-266 degree F.
d. The Oil Filter Bypass Valve on oil filter housing allows oil to bypass oil filter if the oil filter becomes to restrictive.
e. Oil pressure is always available to the Oil Cooler Bypass Valve. Oil flows from the oil pump (past the OPRV) to the oil filter through the Oil cooler and through the Oil Cooler Bypass Valve or directly through the Oil Temperature Control valve when the oil temperature is below 203 deg F. The oil cooler flow return and Oil Cooler Bypass Valve are open at the same time. The oil flow from the oil cooler is never totally blocked (half moon cutout of shuttle valve). The Oil pump flow at Idle is 1.6 gpm and the Oil pump flow at 7,000 rpm is 9.1 gpm.

4. Oil Filter Adapter Functional Details

Oil Temperature Control Valve Assembly.....................Oil Temperature Valve Thermostat opens at 203 deg F


Oil Temperature Shuttle Valve Open (HOT)............................Oil Termperature Shuttle Valve Closed (COLD)


Oil Cooler Bypass Valve Inside........................................ ..........Oil Cooler Bypass Valve Outside
This valve raises the pressure a bit on the flow
trying to bypass the oil cooler making sure some
oil does go through the oil cooler.


Oil Temperature Control Valve Compensation..............Oil Filter Adapter (Oil Temperature Valve Housing)
The orifice allows the valve to move
without being hydraulically locked in place.


5. Oil Flow Paths.

COLD - Oil Temperature Less than 203 deg F.
a. The Oil is pushed up from the bottom Port on the Oil Filter Adapter Housing past the TOP Oil Cooler Port which is ALWAYS OPEN.
b. The Oil then is pushed through the Top Opening of the Oil Temperature Control Valve to the bottom of the Temperature Control Valve Port.
c. The Oil is also pushed against the Oil Cooler Bypass Valve which it will not open since the path through the Temperature Control Valve Port is Open.
d. Some Oil flows through the Oil Cooler back into the Bottom Oil Cooler Port since the Bottom of the Temperature Control Valve has a Half Moon Port that is Always Open.
e. The Oil then pushed up through the Oil Filter Outside Diameter and also against the Oil FIlter Bypass Valve just in case the Oil Filter is too Restrictive.
d. The Oil is then pushed out the center Oil Filter Adapter Fitting (M20x1.5) past the Oil Pressure Sensor for Dash Gauge, past the Oil Temperature Sensor, and past the Oil Pressure Switch Light on Dash Sensor out the Top of the Bottom Ports of the Oil Filter Housing Adapter to the Crankshaft and Top End Camshafts. The Oil pressurizes and lubricates the Timing Chain Tensioners and Timing Chains as the oil flows.
See Timing Chain Idler Sprocket Lubrication and Installation

WARM - Oil Temperature greater than 203 deg F but less than 266 deg F.
a. The direct Oil Path to the Oil Filter through the Oil Temperature Control Valve is not yet closed but is becoming Restrictive.
b. The Bottom Port of the Oil Temperature Control Valve is Opening beyond the Half Moon Port.
c. The Oil Path around the Oil Temperature Control Valve through the Oil Cooler Bypass Valve may come into play.
d. The Oil is then pushed out the center Oil Filter Adapter Fitting (M20x1.5) past the Oil Pressure Sensor for Dash Gauge, past the Oil Temperature Sensor, and past the Oil Pressure Switch Light on Dash Sensor out the Top of the Bottom Ports of the Oil Filter Housing Adapter to the Crankshaft and Top End Camshafts. The Oil pressurizes and lubricates the Timing Chain Tensioners and Timing Chains as the oil flows.
See Timing Chain Idler Sprocket Lubrication and Installation

HOT - Oil Temperature greater than 266 deg F.
a. The Top of the Oil Temperature Control Valve Port Through the Oil Temperature Control Valve is now completely Closed.
b. All Oil is directed through the Oil Cooler (Top Oil Cooler Port) or through the Oil Cooler Bypass Valve around (outside) the top of the Oil Temperature Control Valve.
c. The Bottom of the Oil Temperature Control Valve Port is now completely open allowing Oil to go from the Oil Cooler through the bottom of the Oil Temperature Control Valve directly to the Oil Filter and Oil Filter Bypass Valve.
d. Some Oil passing through the Oil Cooler Bypass Valve will flow directly to the Oil Filter and Oil Filter Bypass Valve depending on the Restrictions to Oil Flow through the Oil Cooler.
e. The Oil is then pushed out the center Oil Filter Adapter Fitting (M20x1.5) past the Oil Pressure Sensor for Dash Gauge, past the Oil Temperature Sensor, and past the Oil Pressure Switch Light on Dash Sensor out the Top of the Bottom Ports of the Oil Filter Housing Adapter to the Crankshaft and Top End Camshafts. The Oil pressurizes and lubricates the Timing Chain Tensioners and Timing Chains as the oil flows.
See Timing Chain Idler Sprocket Lubrication and Installation

6. There IS an Oil Level Sensor on the 91'-95' ZR-1 Oil Pan.

The Oil Pan for 1990, 91 & 92 are interchangable with the only difference being, the 1990 LT5 engine was not equipped with a Low Oil Level Sensor. The extra material was cast into the pan but not machined for the screw-in sensor. As such, the oil level indicator would not be functional if the 1990 oil pan is used for 1991 & 1992 applications Oil Level Sensor TIPS

Brass Oil Level Sensor 93'-95' Jerrys Brass Oil Level Sensor 93' to 95'


Plastic oil Level Sensor 91'-92' Summit Racing Oil Level Sensor
Jerrys Plastic Oil Level Sensor



Last UPDATE of post 18 Dec, 2017

Dynomite

LT5 Lubrication Tricks

1. Oil Pressure Switch Rotated.
The Oil Pressure Switch was rotated 90 deg which allows for easy access.
The additional JIC connection (capped in photo) allows for a Pre Oiler or mechanical oil pressure gauge connection.

Oil Pressure Switch rotated 90 Deg


Background - LT5 Oil Pressure Regulation

The Oil Pressure Regulation Valve (just after oil pump) opening pressure is 50-60 psi Oil Pressure Regulation Valve

The Oil Cooler Bypass Valve on oil filter housing allows oil to bypass the open oil cooler at hot temperatures since oil cooler is a bit restrictive. This valve raises the pressure a bit on the flow trying to bypass the oil cooler making sure some oil does go through the oil cooler.

The Oil Temperature Control Valve on oil filter housing opens oil flow from the oil cooler. The temperature opening characteristics of this valve are Thermostat-Open-203 degree F, Fully open-266 degree F.

The Oil Filter Bypass Valve on oil filter housing allows oil to bypass oil filter if the oil filter becomes to restrictive.

It appears that oil flow is always open to the Oil Cooler Bypass Valve. Oil is not always open directly from the oil pump to the oil filter except through the Oil cooler and Oil Cooler Bypass Valve when the flow from the oil cooler is open. The oil cooler flow return and Oil Cooler Bypass Valve are open at the same time. When the oil flow from the oil cooler is blocked, the oil from oil pump to oil filter is open flow. Oil pump flow at Idle-1.6 gpm, Oil pump flow at 7,000 rpm-9.1 gpm.

As an aside, the after market SS oil cooler lines and aluminum manifold are a bit larger ID than stock with 10AN aeroquip reusable hose end fittings (1/2 inch ID). The 10AN adapter at the aluminum manifold (appears to be M18 x 1.5 or 10AN O ring straight thread) adapts the 10AN ID to the stock manifold hose ID (appears to be 3/8 inch). On the other end at the oil filter housing, the 10AN SS oil cooler line fittings adapt to the 12AN oil filter housing fittings. The stock oil cooler lines have 12AN fittings but smaller than 10AN hose ID.

2. Oil Catch Can.
The Elite Oil Catch Can is attached directly to the front of plenum vacuum source and directly to the PVC connection (use 1/4 inch brass m/m hose nipple) at rear of plenum using SS Braided hose and reusable swivel hose fittings.

Elite Oil Catch Can



a. Used a small steel channel (about 3/8 x 1 x 6 inches) which the flanges are ground to fit the curve of the inside wheel well (at a 45 deg angle).
b. Drilled two 3/8 inch holes in the steel channel to fit the hanger that came with the Oil Catch Can.
c. Drilled two holes to match in wheel well to match.
d. The fit of the oil catch can is very tight against inside of wheel well.
e. Oil Catch Can sits directly above the upper A-Arm rear pivot within 1/2 inch of the pivot.
f. Painted the steel channel black.
g. Used small steel hose clamps on each end of SS Braided hose which keeps hose SS braid from fraying.



The Oil Catch Can Mount was attached using 1/4 inch Wing Nuts for easy removal. The PCV Nipple is 1/4 inch brass male/male installed in PVC rubber connector.
Oil Catch can Elite Engineering USA
SS Braided hose Summit Racing Braided Hose
Hose ends Summit Racing Hose Ends



3. Dipstick Handle Replace.
The Dipstick Handle which is Plastic is usually cracked. I replaced the handle with a Chrome Oil Dipstick Handle



I removed the cracked Plastic Stock Dipstick Handle. Once removed, there is a FLAT with a dimple. I drilled the dimple through with a 5/32 drill bit. I then put that end of the dipstick to a grinder and shortened that end so the hole I drilled lined up with the New Chrome Dipstick Allen Head Bolt hole.


The Chrome Dipstick Handle (5/32" Diameter Allen Head screw with 2.5mm hex Allen head) was then installed using several small brass washers (approximately 5/32" ID) to secure/compress the existing shaft between the two halves of the New Chrome Dipstick Handle.

Dipstick Handle showing 2.5mm Allen Head Screw ...........Chrome Dipstick Handle Installed showing Brass Washers


The existing straight portion of the Dipstick was then placed in a vice and the handle bent and twisted to align the Chrome Handle with the Cam Covers similar to the original alignment.

The New Billet Aluminum Dipstick with BIG RED OIL Letters fits perfectly with the Billet Aluminum Oil Fill Cap I found on Ebay
Search Ebay CORVETTE LT1 BILLET CHROME SCREW IN STYLE OIL CAP Ebay Billet Aluminum Oil Cap (fits 90' & 91' LT5 & L98).




If you place the stock Dipstick in a vice at the flat just below the first squiggles and then with Dipstick Handled INSTALLED...you can twist the Stock Dipstick any direction you want but you have to go over center to make the twist stay. You can also bend the part between the collar and handle but you then have to keep the Dipstick from turning. So it is not too easy for some.......I was about to take a torch and heat the Stock Dipstick End before I figured out that hardened metal Dipstick could be twisted and bent without breaking.

The beauty of the Stock Dipstick is if you break off the cheap Plastic Handle there is a very nice FLAT with that dimple where the outer part of the top part is swedged onto the smaller Flat making a slighty LARGER Flat to work with.

I was going to enclose the bottom of the New Chrome Dipstick Handle with JB Weld but found that not necessary because it absolutely does not show at all until you remove the Dipstick. I may enclose that area with some JB Weld and Rustoleum Black Heat Resistant Paint.

Last UPDATE of post 19 Nov, 2020

Dynomite

Potential Oil Leaks and the OPRV Cover Plate

1. Potential Oil Leaks.

A. OPRV (Oil Pressure Regulating Valve cover plate )......It will appear that the oil pan front bolts are loose and leaking at gasket.
B. Oil Pressure Switch and Oil Pressure Sensor.....
C. Cam Covers.....
D. Camshaft circular rubber plugs (two each end of each Head).....
E. Oil Cooler Hoses/Connections.....
F. There is an Oil Level Sensor on Oil Pan....(not on 1990).
G. Oil Pan Bolts (especially front three 8mm bolts).
H. Center Bolt/Stud on Exhaust Manifold (one each side).
But I would say the one that stumped me the most was that OPRV cover. And prolly the hardest to get at (two 6 mm bolts using an 8 mm Socket wrench).

Marc Haibeck Oil Leak Summary

The most common oil leak is an oil pan gasket leak which is often misdiagnosed. What is really leaking is the Oil Pressure Regulating Valve Cover Plate. It will appear as a drip of oil and oily surface on the right front of the oil pan. Often the tendency is to tighten the front oil pan bolts with no success on stopping the oil leak. The Oil Pressure Regulating Valve Cover leak can also be misdiagnosed as a Front Crankshaft Seal leak. The symptoms are a film of oil progressing rearward on bottom of oil pan or an actual drip of oil on the right front oil pan bolts.

2. Oil Pressure Regulating Valve Cover Plate (1990-1991 ZR-1).

The Oil Presure Regulating Valve is located on passenger side front of engine just above the oil pan. The two 6 mm bolts that hold the OPRV cover plate (and gasket) to the Engine sometimes come loose.



There is an OPRV Cover plate gasket but I just removed and cleaned the two 6 mm bolts (8 mm heads) one at a time and applied Blue Loctite (You could use Red Loctite as you like). I used Blue Loctite because I figured it was a temporary fix but appears to be a permanent fix. I reached in from the top front of the engine to get access to the two 6 mm bolts with an 8 mm hex flex head ratchet wrench. An easier method of access to the Oil Pressure Regulating Valve Cover Plate is from the bottom as described in item #3 below.

Somtimes interlock an open end box wrench (box end interlocked with open end of flex head rachet wrench)
to gain length for that bolt out of normal reach.

Since such a tight area to work in with engine in car I removed each 6 mm bolt one at a time so I did not drop the cover plate or gasket. So...no permatex on that gasket but both 6 mm bolts cleaned and Blue Loctite applied.

Since the bolts and plate were so loose I figured correctly just tightening the 6 mm bolts with Blue Loctite would solve the oil leak and loose bolt problem (The gasket was stuck to the engine block and not the cover plate). I tightened the bolts by feel as I could not get torque wrench even close to that area unless engine is out of car. No more oil leaks in that area at all.

The BEST fix, however, is to replace those two 6mm x 15mm bolts having 8mm heads with two 6mm x 15mm bolts with 10mm heads as described in item #3 below.

Torque for 6 mm bolts is about 89 in-lbs but in that area with no oil pressure to contend with less bolt torque with Blue Loctite or maybe Red Loctite is just fine :thumbsup:

3. Oil Pressure Regulating Valve Cover Plate (1995 ZR-1).

On the 1995 ZR-1 the Oil Pressure Valve Cover Plate is impossible to get to from above because of the EGR. But....one can get to that Cover Plate from below by removing the Passenger side strut that the Passenger Side Motor Mount is bolted to (no pressure on that strut from motor mount). Remove two 15mm bolts toward front and two 13mm bolts on frame rail passenger side. Remove 18mm Nut from Motor Mount Stud and drop the strut. The Oil Pressure Valve Cover Plate can be easily seen toward front where Strut was positioned. The bottom 6mm bolt is easy to unscrew and the top 6mm bolt required a vice grips gripping an 8mm open end to loosen. Both 6mm x 15mm Bolts with 8mm Heads were replaced with 6mm x 15mm Bolts with 10mm Heads.



4. The Trick to STOP oil leaks from the Oil Pressure Control Valve Cover plate.

I replace both top and bottom 6mm x 15mm bolts with 6mm x 15mm Flange Bolts (Ebay and as pictured above) that have a 10mm head for a 10mm Box or ratchet Box wrench. It is a lot easier to tighten a 10mm bolt than an 8mm bolt which sometimes strips in the small 8mm box wrench. I used Red Loctite on the 6mm x 16mm Flange Bolts. No need to remove the Oil Pressure Valve Cover Plate or associated gasket.



Two 6mm x 15mm Flange Bolts installed in Oil Pressure Regulator Valve Cover (10mm Heads)
replacing original 6mm x 15mm (8mm Heads) Bolts.
Top 6mm Bolt shown before tightening with 10mm Box Wrench



Last UPDATE of post 20 Mar, 2018