My 511 is 11.24:1 and runs on MI 93 pump gas no problem.No signs of detonation anywhere. Cam is 270*@50 with a 110* LDA. Not much to gain going as far as 12:1, maybe 2hp, so keep it in the lower 11's. You would have to go to 13- 14:1 to reap any good benefitts of more hp. not really worth it as race gas is very expensive.
