intermittent carb popping 330 GT

Under load, even when warm, my car will OCCASIONALLY get some annoying carb popping at 3-4K RPM, typically 3rd gear, under load. Thats when I notice it most.
Idle is fine. Cruising at 75mph is fine.
I need some guidance- the "occasionally" thing has me puzzled and I dont know where to look.
is this a Fuel mixture, exhaust valve, Fuel delivery, timing or what issue?
michael

 

My first guess, timing curve on one or both distributors. Popping is generally a lean symptom, but it could be a jetting issue with this wonderful stuff they call gasoline today. Welcome to the magic of Weber tuning.

 

Today and yesterday i drove about 100 miles.
I now feel confident its carb related.
Its 3rd gear mostly, light to moderate load. as soon as I step on it, it goes way. the problem is, it occurs in light to moderate traffic, when I can't get on it. so it stumbles.I think its too lean and I guess I need to pull out the weber books, and check out the acceleration circuits. if anyone has other ideas, let su know Thanks brian- I am sure the crappy gas is part of it too. Ill focus on the webers first.
Michael

 

Look at ignition first. Don't fiddle with carbs until you know it's not an ignition problem.

 

I had popping on my 330. A "sunk" carb float was the culprit. One of the brass carb floats had collected fluid inside. I replaced the float, made sure all of the jets were clear, adjusted the idle mix and sync. Not that difficult.
Wise advise to make sure everything else is good first, however, the carb floats can be checked without changing any carb settings.

 

OK good advice. My car was converted to electronic ignition in the 80s, so there are just a few things I can check but I will look that over first.

 

it was a few things-- not rich enough on a few carbs, 2 carbs out of sync with air flow, and the master brake booster service port had a leak so was loosing vacuum on the rear carbs.. all fixed and running great now!