I have a 455 that i'm working on. Looking for some half decent power.
Unfortunately the pistons appear to be 8.5:1 compression. This motor had what seems like a w-30 cam and an offenhauser 360 intake.
I'm putting on a performer intake, not sure on cam yet. How much can the compression be bumped up with either shaving the heads or thinner head gaskets? Thanks in advance.

 

I think it's .006" every 1cc? Consider the stock head gaskets were .017", you'll need at most that thick just to get back to square one. From a google search, it appears .060 is about the max you can go for milling before running into intake bolt and port trouble.


https://classicoldsmobile.com/forums...ads-060-a.html


Short answer, cut the heads .040, run a thin head gasket, 9.0:1 or so....

 

Cut them .060 if that gives you the compression you want. Then just elongate the bolt holes in the intake. Or better yet, surface the intake to match. That's the best way to do it

 

Thanks, not sure what I'm going to do, but I don't want to put a lot of money into this turd! Might run it for now and build a better one later on.

 

How much power are you looking to make? I've run many of the low compression 455's. Ran 12.86 at 3960 lbs. with a stock 71 455 with just a cam, headers, and tuning. Ran 12.18 at 3550 lbs. in my race car with a 76 455 short block, a cam, stock E heads, and headers. Both were stock iron intake and Quadrajet.

 

Wow thats impressive, I didn't think you'd do much better than low 14s with one of these low comp motors in a 3700 lb car!