we did a motor swap from tpi to carb we now have a 350 with 151 cam vortec heads the car will not idle down to 1000 and stray we have notice that the boosters on the 650 db are dripping ga in the main what will cause this. we have tried 2 carbs they both do the same thing ? lets hear from you carb guys.

 

If you pull enough air past the primary throttle blades at idle it will begin to activate the main venturis. It's called nozzle drip and it's murder on idle quality and stability.

Too high a float setting, too much fuel pressure, not enough spark advance at idle, secondary-side idle adjustment not open far enough, etc.

If I had to take a wild guess, I'd say you don't have enough spark advance at idle and you're over-compensating by opening the idle speed screw too far to hold adequate idle speed. More ignition advance at idle will raise the idle speed, allow you to close the throttles further, reduce the amount of air going through the venturis and eliminate the problem while still maintaining a reasonable idle speed.