I just rebuilt my 4100 carb, its on a 390, but it idles rough and I can see and hear fuel dripping from the primary and secondary venturis at idle.onto the throttle plates,

I know its an old carb, probably been rebuilt 2 or 3 times, but it runs fine at high speed, revs good, no smoke, starts fine, drives OK, everything else works but it wont idle smooth. I have noticed the throttle plate blades do not close 100% any more since its such an old carb. Also noticed that the idle mixture adjustment screws do nothing, all the way, all the way out, no change. that tells me the primary idle is doing nothing and the air and fuel dripping past the throttle plates is what it's running on. I thought I cleaned out all the primary circuit orifices and passages but I guess I dont know where all of them are.

any suggestions of how to get the primary circuits working again greatly appreciated !

 

I also noticed the vacuum at idle is NOT good, idle is 19 Inche mercury, should be 24.....that engine normally runs at 24 -25 in. merc. at idle, so theres some leaks somwhere

 

usually when this happens its due to a stuck float causing fuel levels in the carb to be excessively high and the system to run very rich at best