matthon, let me toss this out there, even though I'm not an expert, and if I'm wrong then everybody can correct me.
The problem I have had with those 8.5:1 engines is that they originally came with open-chamber heads, which worked OK because the compression was low, but when you mill the head to raise the C.R. you don't have enough quench and will get bad detonation. So maybe you will have to change to closed-chamber heads.
So if I am wrong about this, then feel free to fire away. I know I need to learn more about this stuff.
