Basic Tune Up Help, Octane Rating

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

Bo,

Are you running real gasoline or ethanol mix? I suggest you try 100% gasoline to see if it eliminates the issues.

I am not a good one to give advice since I am a Buick newbie, but I had/have a similar issue with my '29 model 27 that I bought 2 months ago. In May I changed from a large plastic fuel filter to a smaller metal filter, and from then on after about 3-4 miles of driving I would get popping and small backfiring noises. This weekend I changed back to the "original" plastic fuel filter and test drove 10-12 miles today without a problem --- now I am thinking that the smaller fuel filter was restricting flow too much when the engine was warm.

The fuel I've used so far is ethanol mix, 87 octane, with a bottle of lead additive mixed with each full tank of gas. Others have suggested to me to use ethanol-free gas but that is more difficult to find where I live.

John,

You really don't need the lead additive for a low compression engine like yours.

Try looking here for real gasoline.... http://www.buyrealgas.com/