Originally Posted by fourgearsavoy
I'm just a tick over 10.8 with my 493 Indy head engine. I cant hear any detonation with the pump 93 here in NE Ohio and it runs very well. I haven't checked my cranking compression with my new cam but it seems to run good on pump 93 beer I limit my total advance to 34degrees mechanical with no vacuum advance.
Gus beer

My 518 C.I. pump gas motor in my old Duster ended up having 10.78 to 1 mechanical compression ratio with the set of Indy SR with 76.0 chambers, it never acted like or showed signs of detonation(on the plugs) on Oregon 91 octane pump swill with no ethanol in it back then shruggywork
I ran the same timing as Gus (34 degrees)with no vacuum advance also up

Mr.Cab Racing and winning with Mopars since 1964. (Old F--t, Huh)