72cuttys

I have an unassembled 71 olds 350 that i am looking to rebuild for my cutlass. I am looking to reach ~10-10.5 to 1 compression. If i use flat tops, and a 64cc 7a or 6 head, will i come close to or overcome my goal? Or do i need a piston that has some type of dish to it? I tried using a few calculators but was getting some really wacky numbers. Motor will most likely be worked 6 or 7a heads, a mild cam, and a performer intake.

cutlassefi

With a 6cc piston, zero deck and a typical 6 or 7a head (68cc not 64) you'll have about 9.75:1. If you use the real flat top then yes you'll have about 10.25:1, marginal with iron heads and pump gas.
Wirh either combo I'd use more cam and certainly the RPM instead of the regular Performer.

72cuttys

Thanks! Just what i wanted to hear. We have 93 pump regularly available here so im not too worried about detonation. This is going to strictly be a weekend car, and wont see the upper rpm range very much. Is the RPM really going to be worth it in the lower RPM's?

cutlassefi

With your combo, yes.

captjim

Personally, I would mill .015 off the deck and use the inexpensive .028 Coteco gaskets. That should put piston-to-head at .040. Better sealing and easier. Or, you could zero deck and use .040 gaskets.

ihengineer76

Be sure to cc your heads before you do too many calculations. Most of the time, the 5, 6, and 7 heads were closer to the 67-68 cc range. This can be a good thing, because it will give you some room if you want the heads shaved a small amount to true them up.