[updated:LAST EDITED ON 24-Dec-02 AT 05:02 AM (EST)]I just bought me a new Holley 4160 750 cfm, vac. secondaries just last week, so the thing is still brand new. The instructions said that the factory settings should be good for most applacations, just bolt it on and go. Well I did and it did. Started right up and purred like a kitten, drove well on the street for the last 4 or 5 days. So far, so good, until today. I started it up this morning and it idled smoothly for about 1 min. then all of a sudden it idled real rough, black smoke comming out the tail pipe. Reving the engine had no effect. I have a manual choke so I know the choke wasn't stuck. In fact it's not hooked up yet and I have it wired open to prevent it from closing accidently. I popped the hood, no raw gas smell, everything seemed to be in order. I drove down to the store, ran fine until I came to the first stop light. There it sat, bellowing black smoke from under the truck, wanting to die. People behind me were holding their noses. I had to tickel the throttle to keep it running. Reved the engine, more smoke. Engine at operating temp. When I got to the store, same thing. I'm thinking "now what!" When I come out everything seemed back to normal. It started right up, no smoke, smooth idle. Drove around the rest of the day without any more problems. I'm thinking maybe the float got stuck somehow or perhaps some dirt got in the needle seat, although the inline fuel filter doesn't seem to be too dirty. Dirt in the carburetor can happen to anybody but has anybody ever had problems with the floats sticking on these carbs.? Any other ideas? The model is a 3310S which I believe has center hung floats. Thanks for any and all replies.

EDIT: My truck is a 1975 model with a factory 460 and is not computer controled. Factory fuel pump.

 

I don't have a Holley but it does sound your float stuck open.
People think black smoke from a semi's stack is cool, but it's really just wasted fuel going out the exhaust.
How long since the fuel filter was replaced?
Are you buying cheap gas from a low-rent dealer?