Chop, with the vehicle warm and running at idle or just above, slowly advance the timing at the distributor and listen to the engine. You'll reach a point where the engine's idling does not continue to improve,smooth out. Back off slightly and try it.
I've got a 235 with an RV cam, two single barrel Rochester's on a Fenton intake and headers. I've had a number of "opportunities" to get this system running smoothly. Other issues to think about could be:
Do you have vacuum advance on your distributor? If not you need it.
Are the carburetors balanced using a Uni-Sync?
Have you verified your system does not have any vacuum leaks by using starting fluid to check your carb and intake connections for leaks?
Good luck and have fun,
Ted
