I've read dozens of threads about timing, but have yet to sort mine out. Maybe just one more thread on the subject will get through to me.
I destroyed my last engine via detonation..and I never heard a thing. The current engine, I DO hear it once in awhile. The only way I've gotten completely rid of it: VP fuel, Trick fuel, or adding toluene to pump 92 octane fuel.
Engine specs that matter: 62cc heads (measured), 9.9 compression ratio (by the math of measured volumes, designed low to run on pump gas), HE3844 cam, A833, 4.56 gears, Holley 750 4-post idle set by vac and butt-in-seat gauge, mixture band on plugs is perfect..a bit rich, Performer RPM air-gap manifold, Mallory distributor with 20º in it..spring color I don't recall, but stiffer than it came with...all in @3000rpm, 11º vacuum can (adjusted from one limit to the other, will still ping). I hear it most often around carb secondary start (2nd pump clearance set to nil at rest).
