I have a stock 72 olds 455 believed to be 8.5 compression. What gains Hp & torque would I gain from bumping from 8.5 to 9.5 or even 10.1?

 

Depends on what you do to the rest of the engine. If you plan to bump the compression you would also be looking at a new cam etc. Everything would have an effect on power.

 

So if I just want a fast weekend car is this something I should even be worried about? My thing is I bought a motor that the guy knew nothing about, he just wanted it out of his f-150 a.s.ap. because he is a ford guy. I bought the motor for cheap not knowing any history other than it's a 68-72 block with 72 Ga heads and I heard it start while in the truck but I never drove the truck. So I took off the heads (had big dish pistons) and pan last night and the inside of the motor looks rebuilt, was very clean, no sludge in oil pan, cylinder walls look machined, and rods are number stamped. The only weird thing was that it had the thin metal head gaskets. Since I have the motor on the stand I was debating if I should just paint it and add after market bolt ons or if I should redo the motor to boost the compression and change the cam. I'm looking for 350 - 400 gross HP 500f ft pound torque. Any suggestions or if you can help me make a better choice will be appreciated. Thank you all..

 

Sounds like the rebuilder was also trying to increase compression, too.
Earlier heads had smaller combustion chambers, hence more compression, but, I'm not sure which would help more.
I'm sure others will chime in -

 

Well, if you go back with a fel pro fiber gasket, which btw is thicker, you will reduce your compression by .5! The steel gaskets are to find but there are some out there! A simple cam, headers and a good quality 2000 - 2400 rpm stall converter would probably give you a fine pants in the seat performance upgrade!

 

compression from 8:1 to 9.5:1 / 10:1 would increase hp by roughly 20 theoretically.

edit: 10:1 probably 30

Running 91+ fuel also would aid HP with such high compression