I talked to an engine builder a while back about this but only in slight detail so I don't have much to add here, but I will raise a question. I wish now that I would have talked to the guy more in depth about the subject. So this builder had a race engine that he claimed by changing the cam in, he changed the cylinder pressure from 300 psi to 180 psi. All by changing the cam (with more overlap or something I assume). So here's my question, say if you have an engine that is STATICALLY 12:1 or 13:1, but your cylinder pressure is only around 180 psi with the camshaft combo, could you really run 91 or 93 octane?