383 with 10 lbs. boost,water/air cooler 8:1 compression,Eddy heads, 91 octane pump gas. I run 12deg. initial and 25deg. total and on a 95 degree day last summer it would very briefly clatter on the 1-2 & 2-3 shift.I'm talking about 2 audible knocks in about 1/10 of a second. That's probably about all the detonation the cast pistons can stand.
