Carb popping on a 330 GTC

I hope someone can help with what seems like a simple tune-up problem, but one I can't solve. I had my carburettors rebuilt earlier this year by Pierce Manifolds. I had problems with the throttle shafts sticking due to warped bodies. After replacing the carbs I reset the points, checked and set the ignition timing (12-14 degrees advance). With the motor warm I synchronized the carbs (Uni-syn) and then set the idle mixture with a Colortune. The idle mixture screws were all set rich after the rebuild. The problem is that anything more than a gentle push on the accelerator results in popping from the carbs even when warmed up. I have occationally experienced this popping before with a cold motor but not to this degree. I use 94 octane(10% ethanol) gas in the car. Any idea if this is a timing issue, mixture, combination, none of the above? Your suggestions are welcome.

Hi Bruce,

Have you checked that

1- the Distributor Advance Mechanisms work...and work the same on both banks?

2- the accelerator pump nozzles squirt gas into throats as soon as the throttle linkage starts opening?

Those are the two items that stand out in my mind intially. If the engine is missing on several cynlinders for one reason or another this could also cause something like what you describe. Also "intake leaks" either from warped carb bases, using old base gaskits or hardened intake manifolds o-rings.

Think about those items and do a few checks.

Regards, JRV