I have the stock holly 2bb carb on my 5.9l 1975 W200. The truck was running fine until I ran it out of gas and let it set for a while. Now it won't idle at all. When the engine is cold, it will start right up but idle very rough. After a few minutes the idle gets worse and worse until it stalls out. If I rev the engine, it will run great, and is very responsive. However, as soon as I let off the gas, the truck will stall out, and is almost impossible to start, even with starting fluid. I think it's getting flooded with gas, because if I keep the throttle wide open it will eventually start after a lot of cranking, but the battery usually dies before it will start. I already replaced the spark plugs, wires, and cap and rotor, and it's getting great spark.

I was looking at the carb today and noticed that the top of it was filled with gas. That doesn't seem normal to me. I also noticed that when the truck was about to stall out, gas would start gurgling up out of the accelerator pump (the red circle in the picture). As soon as the engine stalls, the gas would get sucked back down into the accelerator pump. What's going on here? The only thing I could come up with is that my float level isn't set right and too much gas is being pushed into the float bowl. Any more suggestions?

 

maybe the float is sticking. you could try tapping on the float bowl with a screw driver handle.

 

That's what it spinds like.
Excuse the misspelled double post.
Merry Christmas.

 

That's what it sounds like.

 

I think what you have circled is called the bowl vent. Could be a sticking float, a sticking inlet valve, or crud that is keeping the inlet needle valve from seating properly.