bowtie350_428

I have AFR 190 heads (P/N 1015) which have a 68 cc chamber. With my combo, this gives me 9.4 cr on a 350 SBC. I would like to know if it is possible and safe to mill the heads down enough to get a 64cc and use a .027 gasket to get 10.1 cr.

Questions:
How much would I need to mill my AFR 190 heads get to 64cc? How far can they be milled safely?

Also how safe is it to use a .027 head gasket for the street and daily driving? Can someone recommend head gaskets in this range?

Thanks

bowtie350_428

BTW, here is my Compression Ratio Data:

Current cr:
Cylinder Head Volume (cc) = 68
Piston Valve Relief (cc) = 6
Gasket Thickness (in.) = .039
Gasket Bore = 4.166
Cylinder Bore Diameter = 4.040
Deck Clearance = .019
Stroke = 3.48
STATIC COMPRESSION RATIO 09.433

I would like to have:
Cylinder Head Volume (cc) = 64
Piston Valve Relief (cc) = 6
Gasket Thickness (in.) = .027
Gasket Bore = 4.166
Cylinder Bore Diameter = 4.040
Deck Clearance = .019
Stroke = 3.48
STATIC COMPRESSION RATIO 10.138

thanks

mr.beachcomber

First I would recommend contacting AFR and ask them how much milling/angle milling they would recommend for their heads.

BTW, your static compression ratios are close, but I don't think you are adding in the volume for the gasket opening around the piston. For example, my calculations were 10.1347:1 for your target goal. (If you're really looking for an accurate static volume ratio, don't forget to add the volume for your spark plug by cc'ing the chamber with the plug in place.)

Your quench value for the target static compression ratio is 0.046", just outside the box of the recommended 0.040". (Better quench provides better swirl and mixing which is crucial to avoiding detonation at higher compression ratios.)

See what AFR recommends for milling and balance that cost against zero decking your block which would give you a 9.8377:1 compression ratio and a quench of 0.039" with your current gasket. Just my recommendation, YMMV.

Good luck with the mods!

rklessdriver

You need to loose 4 cc's. It normally takes .007 of milling (off the deck surface) per cc so you need to mill the heads .028. AFR's will mill that far no problem.

You MAY get into the intake seat at the dept. If you do, the valve job will need to be touched up.

I prefer to run the .026 Victor head gasket on GEN II LTX engines. It is a composite gasket and is very forgiving of deck surface finish unlike some MLS gaskets. I've used many of these gaskets over the years and none have ever had any problems.

They make the same gasket for GEN I SBC's. Victor Reinz PN 5746.
Will

Movnviolation

AFR milled my 180 comps to 58 cc with no problems maintaining my 10:4 compression. Contact them!

bowtie350_428

I did not know what you meant by “quench”... That is until I googled it. Interesting stuff. I guess I also need to worry about the little gap between the head a piston at the opposite side of the spark plug as well.

Zero decking the block is another option I was considering but it would not decrease combustion chamber volume. But now that you bring up quench, I may consider decking the block in comination with milling the heads. And use the head gasket to dictate the quench value and keep it close to .040.

I guess getting in touch with AFR is also a good idea.

rodj

No , but it decreases the volume above the piston increasing your compression the same as reducing the chamber size .When calculating CR , you have to take into account as you have done ,every thing above the piston;
including the dish size in piston , how far down the bore the piston is , the bore size of the head gasket , the thickness of the head gasket and the chamber size. Reduce any of these and you will raise the compression.
Do your calcs with a gasket with 4.060 bore ( less dead area in quench zone ) and see what changes.

Red Rocket

Impala LT1 Head gasket is used by alot guys, .028 thickness. Part# 12553160.

bowtie350_428

Milling .007 = 1 cc ("normally") Thanks rklessdriver, thats what I was looking for.

The Victor .026 gasket sounds good. So does the Impala gasket at .028 (P/N 12553160) mentioned by Red Rocket. But they are both for LTx type engines. Would I have any problems using them on an Gen I SBC?

GREGGPENN

Yes... you need a Gen1 SBC gasket. TPIS sells the Gen1 Victor. I also found it for less on CNC-Motorsports website.

bowtie350_428

Thanks GREGGPENN!

rklessdriver

The Victor part number I gave you IS for the GEN 1 SBC. Sorry if I confused you.

CNC-Motorsports is a good place to buy from.
Will

bowtie350_428

Sorry, I just re-read your post and you did indeed state it was for a Gen I. Thanks rklessdriver!