I have alum heads and run California 91 Octane. I’ve got 9.7:1.
I’m on the edge of pinging. On a 95 deg day going up a steep steady mountain I had slight pinging (sounded light). I backed timing a deg, plugs, carb adj, and all good.
Imho, that “one full point compression increase with aluminum heads all else equal” is a false general statement. Especially with more street friendly cams.
