1993GMCPU

Trying to raise 76 cc compression based on CNC shop of .059 equals 1 cc. ANY way any thoughts on doing this in truck?

Using H345NP40 pistons (40), .015 Fel Pro 1094 gasket, and had heads cleaned up .020, using a 12-402-4 cam and 1.94-1.50 valves what would my compression?

Over 9.0:1 a least and hope, so more cam options but under 10.0:1 would be cool. Quench 40, so this should help for now and I can a least move the truck.

Thank YOU for your help!

F-BIRD'88

Based on your numbers , with 76cc heads your compression ratio would be 8.8:1.
If you flat milled the heads .060" you typically end up with about 68-69cc's which would get you 9.5:1 at best.

Those piston are normally .045" down the hole on a stock block that has not been decked.
If you decked the bock .025" and shaved the heads the same .060" you would have 10.08:1 if you deck it .030"
you would have 10.2:1
Your quench clearance including the .015" gasket would be .030". This is about as tight as you can go without the piston smacking the head at high rpm.

You may have to shave the intake manifold mating surface on the head and the bottom surface on the intake to restore the port alignment after all this decking and shaving. The rule is shave the manifold mating surface .125 or every .100" off the head.
You'd want to mock it up first to see exactly how the alignment is after shaving the heads though.
Port matching the ports (raising the port roof) and enlarging
the manifold bolt holes is often all that is nessessary.

RB83L69

.060" is ALOT to take off of stock heads, especially typical "lightweight" smog castings. You might be wiser to go find a better set of heads in the first place, rather than to spend money on polishing up those turds, put them on there, and then have them crack.

F-BIRD'88

Yes .060" would be the max you would want to shave them.

You'll get better results for the same $$ or less $$'s by starting with a small chamber (305 head) and upgrading it with home porting and larger 350 sized valves.
These heads are a dime a dozen. (416 castings)
Sell off your 76cc heads.