The DCR on my 340 comes in at 8.195 and I have to pull timing to run 91 octane with iron heads. Static compression is 9.8:1. It’s only a couple of degrees, but it detonates if I don’t pull that timing. Pistons are over the deck on my build, quench isn’t perfect or anything so I’m not saying you can’t do better than I do. But if you go past mid 8’s on the DCR I’m not sure aluminum heads will save you. Not with the gas I run anyway.
I’m with Steve too, those numbers don’t look right.
