Hello, I have been offered first dibs at olds heads.
What ones would help with power production on a 1975 stock 350 olds?
If I get the heads, I'll swap in a cam while it is apart. but what if any olds factory heads will maybe up the compression from the mid 70's dumpster fire comression ratio?
Thanks for your time.

 

Oldsmobile engineers used various piston dishes to determine compression and its not so much the design or casting of the heads. There is only so much you can do to decrease the combustion chamber or deck surface to increase compression. And then, you'll have to machine the intake or intake side of head to get the intake to seal.

If I had a choice, #5 #6 #7, in that order, for a 350. I too, would skip the #8 that you probably have now.

 

I think #7's have hardened valve seats and I know 7a's do. Of course now that may be a moot point after possibly having several valve jobs.

 

Pick the early heads in the best shape. By the time you add Felpro gaskets, you will only have around 8.5 to 1 compression, unless milling is done to the heads or they have previously been cut.

 

That was true in the early years, but the 1973-1976 #8 head combustion chamber was larger than the earlier years. The good news is the piston dish was reduced to keep the CR at 8.5:1. The '71-'72 350s had 8.5:1 compression ratio using HUGE 24cc piston dishes along with the approximately 68cc combustion chambers (same for all 68-72 350s). So using the earlier smaller combustion chamber heads along with the smaller 14cc piston dishes can be beneficial. You have to be aware of all the tolerances as noted by olds 307 and 403 above.

 

I'm not an expert, but you better not overcam without raising the compression. And anything other than the stock steel shim head gasket (unobtainium) will result in lower compression. Experts, chime in please.

 

I ported some #5 heads and had a 3 angle valve job done when I had my engine rebuilt.
New cam with dual exhaust. Engine really woke up.