Hi everybody. need some simple advice fo my '41 Super, dual carbs. Car running well, compression ~95lbs, dwell at ~31*, valves quiet. Shop manual..timing at 2*BTDC...haven't done that yet, but have adjusted by ear/tach. Wondering what impact octane rating makes. Owners' manual recommends 70 octane. As I eae off the accelerator ...on a hill or otherwise...there's a great deal of popping/light backfiring at the exhaust. I've had many opinions from buds, thoug not Buick guys...timing too far advanced, timing retarded, too rich mixture, bad valves, points not adjusted...you get the idea. Any insight or suggestions? Thanks in advance, maybe see you in Portland. vr Bo '41 Super Coupe