Help, I just left a friends house. He has a 396/325hp basically stock with Edelbrock intake, Holley 750cfm and headers. Float levels are good now but wasn't. Had dumped a bunch of gas in the carb. Timing is at 14 degrees, appears to jump on occasion but we had a cheap timing light. The ported vacuum will not activate the vacuum advance (5in). We moved to the manifold advance (15in). Definitely improved. Also developed a rubbing or rattling sound in or around the motor. Plan on changing the oil & plugs tomorrow. V-Groove Accels. Could the gas that went down the carb still be causing problems? Thanks in advance

You might double check your dwell setting on the distributor. When we rebuilt my 350 we were having almost the same problem, backfiring on accel, very rough idle, and wouldn't stay in time. We finally checked the dwell and it was about 20 points short of what it was supposed to be.

Don't forget to recheck the timing if you change the dwell.
Fred

If the carb was dumping a bunch of gas the plugs are very likely to be fouled.

Definately clean the plugs while your working on it like Steve said.