Old hat...

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).

I've been running 12º initial timing @1000rpm, total mech of 32º (like I said...dist has 20º in it). I asked the folks at Hughes Engines about it. They suggested that 12º was too much, that it would build heat in the engine that might help detonation happen. They also said the idle needed to come down. Set to 10º/30º and an idle of 800rpm: Still some rattle.

My question: Other small block folks here say 'more is better (if the engine likes it)' and talk of 15-18º initial, 36º total. There is NO way I can run that on pump gas. The engine runs better with a higher initial timing, but that would mean taking the distributor down to 15-17º or so.

I don't recall that low a mechanical advance ever being used. Does it sound reasonable?

Thanks!