One more thing to check if you have popping in the carb is the spark plug wires. Make sure they are in the right order. A couple of plug wires crossed will make it pop.
I don't know that a vacuum advance line leaking would cause you problems with idling, but worth a look. But seems to me the only time vacuum is applied to the advance is when the throttle is opened, so shouldn't be any at the distributor at idle.
As mentioned, valve adjustment could be off. A bent push rod on a newly rebuilt engine is possible too due to a valve guide being too tight. If it's on a exhaust valve it will pop back through the carb.
Last edited by Roy Rodgers; 11/15/2013 1:14 PM.
