After struggling with what I believed to be a Weber carb jetting problem for longer than i care to admit it was suggested that the problem is not jetting at all but rather an ignition problem. Which could very likely be the case.

Here's the situation: b20 block bored .030 over, D cam, Pertronix ignition, Weber carb, F head with injection ports plugged, 2 into 1 exhaust 2.5". Ran fine in my son's 144. Transplanted into my 544 and the frustration begins.

Symptom: When warmed up and under load it pops, snorts and backfires thru the carb in 1st and 2nd gear. My first thought was a lean condition which could be remedied with a jetting adjustment. Timing is set at 10 degrees BTDC. Any other timing setting seems to cause even more backfire out the exhaust or the carb depending which direction I move the timing.
When I have the timing light on it and I rev it up it seems to 'hunt' a bit before it settles back down to idle at 10 degrees.
I have not found any vacuum leaks and the vacuum advance on the distributor is plugged off.

Thoughts? Suggestions? Ideas?