[Formulajones]

Originally Posted by GoreMaker

I recently revived this one from the distant past:
http://www.projectpontiac.com/ppsite...tio-calculator

The rest of the site is a decades-old irrelevant mess, but the dynamic compression ratio calculator is still valid and useful. It's remarkable to see how a different cam results in completely different actual compression ratio, which is what really matters when it comes to octane. This is why some people can get away with running 91 octane with 10:1 static compression and iron heads, while others will be pinging with 9.25:1 under the same circumstances.

Yep, that's how I'm able to run 11:1 with iron heads and 91 octane