My85IROC

I need to know if anyone has had problems with valve clearance when using AFR 190, 68cc chambers with SLP or KB forged flat top pistons with valve reliefs. The cam I am looking at has .525 /.525 lift

My85IROC

Somebody??? I know there are some of you that have these heads. I just want to know if you had any clearance problems.

kevinc

I'm running AFR 190 L98-angle plug heads, angle milled down to 58cc chamber size, with 0.525" lift HOT cam.

Pistons are Federal-Mogul flat-tops with 2 valve reliefs, part# is H631P. I measured clearance at max lift, don't have the numbers handy, but it was well outside the limit.

So...if your KB pistons' valve relief is anywhere near as deep as the FM pistons, should be no problem at all.

My85IROC

Thanks for the help. My figures are that there won't be a problem as well but I am trying to avoid problems and additional cost.

Thanks again.

kevinc

Are you sure you want to go with 68cc chambers? I didn't see if you're planning on a blower or turbo...for NA that will really drop your compression.

DTL504

iTrader: (1)

A better choice will be to use the 74cc heads w/ flattop pistons to keep your compression low, if you use the 68cc and flat top you will run a high compression and will linit the use of street gas or higher octane rating. You will need to check the valve to piston clearance after you mock the engine. Different engine will have different clearance depending on the gasket, deck height, and cam. You can use some modeling clay to check the clearance and spray a little WD-40 on the clay strips to keep them from sticking.
If you need more direction just let me knoe i have a few article on how to do this.

DTL504

kevinc

58cc chambers, 2vr flat-tops, factory deck height, 11.2:1 calculated compression, and 89 octane gas for street use. The way to do it is to tune the spark map carefully and be willing to give up a few HP (but not likely as much as w/ 74cc heads and 9.x:1 compression) when running the 89 octane juice.

It really likes 93 octane and a few extra degrees of advance, can't wait to test with 100+ octane racing fuel this season.

I don't disagree w/ what you're saying, but I can tune chips and upgrade fuels much quicker than heads.

My85IROC

I am aiming at 9.7:1 to 10.0:1 compression. I don't plan on a blower but may use a small shot of N20.