[Brent Flynn]

Originally Posted by Cliff R

My first 455 was 10 to 1 with iron heads, zero issues anyplace on pump fuel, even 89-90 octane.

I increased the CR on that engine to 10.48 to 1 with KRE heads, custom HR camshaft, zero issues anyplace.

The current engine is 11 to 1 and runs easily on 89 octane. I've even put 87 octane in it and no pinging anyplace.

For the average Pontiac "street" engine, no need to put a lot of compression into it unless you have goals for the project that include running really quick at the track, and you plan on taking the needed steps to effectively manage higher compression on pump fuel.

The cam is equally as important as the static compression ratio. The 9.5 to 1 limit we keep seeing regirgitated on this website is absolutely a retarded statement, IMHO.

I've had engines in here to tune at 9.5 to 1 that rattled like SLEDGEHAMMERS just about everyplace because of a poor cam choice.

I've built engines over 10 to 1 on iron heads and some of them are out there over a decade now with ZERO issues anyplace on a steady diet of pump gas.....Cliff

So...is it longer duration, wider lobe separation, lobe profile or amount of overlap that enables higher compression engine to burn 89 or 93 octane? My engine in my Bird right now is .030 455 w/#62 heads ... i know my cam is .503 Engle from 1984, either 106 or 108LSA, and would love to try somethin else and maybe street drive this engine some...