I have an olds 403 that is bored 0.24 over with the kb pistons. i have 72 7a heads that are already all machined with port and polish job and the biggest valves possible. Im afraid my compression will be too much. i think it will be around 11:1. I dont mind running and octane booster. I havnt had these heads flow tested yet but im hoping they will support 500 hp. Can i use theses heads or am i better off going with the 455 c heads?

 

you're gonna need way more than octane booster with that comp. ratio on an iron head.

 

You need to figure exactly what it is. Don't take anything for granted. Whats the dish in the piston? Head CC?