douglyle

I'm looking to buy a big block coupe and could use a little advice. What engine is better for steet driving? I've heard varying accounts of what motor is better. Some people tell me the L36 will run worse on pump gas than the L72. I realize I'll probably need a lead type additive to boost octane levels and will possiby need to add hardened valve seats. Besides fuel requirements I'd just like to know what motor is a better driver and why? I've read all the books and know about specs, solid vs. hydraulic cams, 4 and 2 bolt mains, etc. I would really appreciate hearing from people who own and drive with these engines. I plan on driving this car so drivability is very important.

And if you're selling one of these please contact me.
thanks, Doug 408-593-7375

Vetterodder

Octane requirements are close to the same for either. The bigger cam of the L72 reduces cylinder pressures some (as compared to the L36) which would offset some or all of the effect of it's higher cr. The L36 has better low rpm torque but the L72 still has plenty unless it's pulling tall gears. If drivability is a priority for you, it probably wouldn't make sense to pay the premium for a L72 car over a L36 car unless for other reasons. If either engine is in good condition and properly tuned, premium pump fuel should be ok without any "snakeoil". Unless you plan to use the car way differently than 99.99% of Corvette owners do, don't worry about hardened valve seats.

Blkblt

I've been driving an original driveline (to the best of everyones knowledge) L72 (with some modifications) for about 6 years now at 3-4k miles annually, and its been a pleasure with few problems. Generally it eats only pump 91 oc (except during winter and early spring when I go with 100 oc as our winter fuel in Colorado is just junk). That being said, the last owner detuned the motor with a hydraulic cam, did the heads, and lowered CR into the 9s or very low 10s somewhere. I have added an 850 BG mech sec carb (perfectly adjusted and tuned by Lars Grimsrud) and MSDS 6a ignition system to assist driveability. I also installed an underbody Sweet Thunder 2.5" chambered exhaust system to keep the neighbors awake. The car now dynos very comparable with an L36 (which another CCCer drives and has dynoed), and puts out something around 425+ BHP adjusted for altitude. At this altitude my 0-60 times are in the high 5s-low 6s. I have taken this car to the Black Hills Classic in 102°+ temps and all over the mountains of Colorado to altitudes in excess of 12,000', and have never had either a driveability or heating issue (one time it did heat to just over 215°....big deal, and its a real dog at 12,000', just like me). This particular car fires immediately even in cold temps and idles down to 750 without attendance (again due to the MSDS and a perfectly adjusted carb...which is very critical). Gas mileage sucks, but I didn't buy this car to baby for mpg.

I am a big block guy and have had great luck thus far. The car is a bit slow for me, but that will be rectified in time.... This is just my experience. Others will have both similar and opposite things to say about BBs. Some don't think they are driveable in the least!!

Good luck and

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Jeff; Charter CCC
1966. Modified L72
The Silver Beast

Ironcross

Best choice. 427 L 72`s first rated at 450HP and then reduced to 425HP for company reasons is one of the nicest single 4 bore carb engines built. Yenko, Berger, and a few other dealerships used these engines in their conversion Camaros and Chevy two`s. The engine needs nothing except premium gas and runs trouble free like a deer. Actually the 66 Vette L72 equiped was considered one of the quickest Corvettes ever.

67435animal

Doug, as folks have said above, either should run fine. However, if the car you buy needs octane, please don't waste your money on boosters (increase octane by 8 points !! really means by 0.8) and, they leave a nasty rust deposit all over the upper cylinders.

If you need octane, the only way to go is racing fuel. If you are interested in a 67 435 coupe, PM me.

aworks

I have a L36 66 coupe. Orig. motor and bone stock. It is a great running car and excellent to drive. I have backed out the timing just a hair and it runs ok on pump gas. But you can tell the diff. when you add some race fuel. As far as performance. Its a pooch. Compared to my other cars the 390Hp 427 is just slow. That being said I love the car and love to drive it. It is smooth like driving you mamas car.If the car was not so orig. I would have changed the cam and intake plus some head work.

66427-450

define how you plan on driving it...RPM range, etc.

the 390 is a great all round engine for moderate street perf use (read; more torque at lower RPMs). the 425 can be a real butt kicker with the right gears/tune.... both are crying for better exhaust systems

douglyle

I don't plan on racing but of course more hp is always welcome. I had heard stories that the 390 would run worse than the 425 on pump gas. Most of the driving will be around town so I assume I'll be in the lower RPM range around town. I've got a thread going on NCRS about this same topic and it seems from what I've read both engines are great. I think I'm leaning towards the 425.

Doug

66427-450

well, as far as i'm concerned....

if you're into power steering, air, 3.36's, "crusing", etc.... think 390

if you're into 4.11's, 0-140 MPH blasts, and want serious power from 4000-7000, think 425. e.g., the heads on a 425 really don't start working good till ~4500 revs

just one opinion.... of course i think 425/450's are the only way to go :-)

66427-450

it's all about getting the advance curve/profile setup just right....... both will work with pump gas.

StrayDog

Words of wisdom from a big/bloc owner My 1966 , 427, has wide ratio 4 speed... vintage 1966 block ( re- stamp).30 over now 433 CU IN >>> the previous owner radically de-tuned it......I thought it had the 390 L36 cam .. ... I took her apart for a rebuild discoverd a Crane 250 deg hydralic cam............as my 66 is a street driver with stock side pipes & 3.08 rear gears (no hedders)...I rebuilt for 1300-5600 RPM range...installed a comp cam XE 262 short duration high lift cam, (very strong mid-range) pulls hard to my self imposed 5,700 red line.......installed Endlebroc oval port alum heads, MSD dist & 6200 box, Comp Cam 1.72 roller tiped rockers,0riginal stock 780 CFM Holley, the pistons are TRW 2300F small dome , the block was redecked as she needed to be trued up ...compression ratio 9.8.....runs great on 93 octane, (did all work myself as winter projects) with 3.08 high way gears consistently pulls 13.3 ET @ 105 MPH.............have since installed 3.70 gears will go the 1/4 mile in the spring , have a set of street radial drag tires looking for 12.99 et.........I have owned my 66 for 11 years >> IF << I did it again (engine modifications) would have installed 440 HP 454 Chevy crate engine & saved mucn money ............I have all original parts on the shelf >>> my engine looks bone stock with exception of aluminum heads...so all this babble is take your time with what you intend to do ...dont go crazy with an extreme cam , keep compession ratio below 10 to 1 & think of your driveing range .. you will be happy with high mid range tourque that you need for the street ...the babble of the DOG workjed for me..Woof :thumbs or you could leave absolutely stock...what sense has all this advce been ..dont know as I have cabin fever 3 feet of snow outside