Packard Twelve carb popping

[Guest rwoolfitt]

Looking for a solution. I've had intermittent popping back from the carb, now made worse by doing maintenance on the car. I have new dual coils, new points, condensers, plugs, plug wires and have rebuilt the carb. The car is timed. It runs fine up to about 45-50 mph, but cruising above that "causes" back-popping through the carb (no explosion in the muffler). This does not occur when revving in the shop, but only under load. It is "cured" by slowing down or stepping harder on the gas. I have good compression and no gasket leaks. Looking for any ideas or suggestions. Thanks. Bob (rwoolfitt@cox.net)

[nickelroadster]

Sounds like you are running lean, probably due to alcohol. Richen up your mixture a little bit . You don't say what kind of carb you have.

[Guest rwoolfitt]

Thanks for your suggestion. It's a Stromberg EE3. I'm the first to say I don't know much about carbs, but I did put in ethanol-free gas and it didn't seem to make a difference. It only seems to happen when I'm just cruising along. Also, I can make it go away by accelerating. I'll check into making the mixture richer. Thanks again. Bob

[Guest cben09]

Is there any reason to suspect weak valve springs,or stickey valves ,,The hydraulic silencers would maybee,,expand at speed

if the springs were weak,,,Find someone familiar with this engine,,

Retard spark would promote this if it were on the edge,,

Just some thoughts,,,Ben

[Guest rwoolfitt]

Many thanks for your thoughts. I have asked people who know Packard Twelves and they are mystified too! I do appreciate your taking the time to write. Bob