Carb Drip

Have Grandsons 340 with 509 cam and a AVS Carter 4 BBL. At idle (about 1000 rpm ) the ventures are dripping droplets of raw fuel. I rebuilt the carb and same problem. Removed the carb and readjusted the floats and still have same problem. Can anyone help with an answer or cause to the problem. Also Idle is unstable at times and mixture adjustments make little differance. Thanks ron