Ok, running factory cast iron F heads on a 455, using 91-93 octane fuel, what determines the max compression ratio piston you can use comfortably on a street car at sea level? I am told the 328 w30 cam bleeds off enough cylinder pressure to use 10:1 but I from everything I have read 9:5-1 is optimal, others say not true..looking for expert knowledge.

 

I’ve run 10.0:1 with newer cam tech and no issues, IF it’s tuned correctly. That’s the key, the right overall combo. You can detonate an 8.0:1 build just as easily if things aren’t right too.

 

So the general rule about compression always comes down to tuning? I read all kinds of crap stating nothing over 9:1 etc. I built a 421 pontiac at 9:5-1 and no pings, runs great, cast heads.. I have spoke with you before Mark on cam info. I have to take my block in and get it checked, its 0.30 over but when a rod bearing spun there is a very minor scar on one cylinder, Not sure if it can be honed out, or will have to be bored 10,000 to 40 over to clean it up. That’ll be later this summer then I’ll be getting with you because I’m going to need pistons , cam to rebuild that short Block especially if it’s has to be bored.. I just don’t want detonation issues so if I have to sacrifice 20 hp that’s what I have to do. Also the clearances I’ve read where W30 had a lot more piston to wall clearance than the stock for 55? What is the correct clearance on a street car rebuild?