Dynamic Compression Ratio - this will be a good indicator if you can run on pump fuel.

I run around 9.6:1 cr with Eddy aluminum heads and 32-34* total timing in my 470 low-deck. 259/267 @ .050 / 110 lsa camshaft.

No reason to go big on compression with pump gas, if I'm losing 3% +/- per point, i'm not going to risk detonation and pull timing as a band-aid.


In a street car, we all know the load is variable, if you've ever watched a wideband air/fuel gauge, you can see how quickly an engine can go from rich to lean, varying on throttle position, transitions, and multiple other factors; it's nearly impossible to tune a carb to be perfect in all conditions year-round. In a race car, the load is somewhat constant, simply tune for WOT - 12.5:1 +/- AFR. Make it fat, lean it out.

Detonation destroys engines, if it's not a bracket / race car, stay on the lesser end of the compression spectrum and run as much timing as needed.