I need some help; I have an 83 Z28 that has a Holley carb. I bought the car like this so I am not sure what model of carb it is, I don't see any ID #'s. It is a double pumper, as it has two fuel inlets. Here is my problem, and it just started yesterday. The secondaries, which are in the back, are dripping raw gas at idle, and is flooding out when driving. I can see it doing this, however I don't have a clue as to what I can do about it. It would seem to me that the float is sticking open. Is there anything that I can do without tearing the whole thing apart? Is there a float adjustment that I could try? There are two large screws on top, one on the front and one on the back, would these be an adjustment? I apologize that I don't know the model, and I don't have a digital camera either. This is my daily driver, and college just started back up, so I need to get her going! Any help at all would be very appreciated! Thank You

 

2 lines does not equal double-pumper. Not that it matters very much in this case.

The 2 huge nut/screw things are the float adjustments. The way to adjust them is to start out with the car turned off; remove the sight plugs on the sides of the fuel bowls; hold the screw still with a large screwdriver; and loosen the nut. Turn the screws in (tighten direction) about 2 turns; re tighten the nut. Start the car. Let it idle for a while, and rev it a few times to drain the secondary bowl somewhat too. When fuel quits spilling out the sight plug holes, very carefully hold one of the screws still again, loosen its nut slightly, and while holding the nut still, back the screw out slowly until fuel just starts dribbling out of the sight holes. Then turn the screw back in about 1/8 turn, and tighten the nut, and do the other bowl. DO NOT loosen the nut more than just barely enough to let the screw turn using a really big screwdriver with the car running, gasoline will shoot everywhere. This is not a fun situation.

Ideal adjustment is usually to where fuel doesn't come out of the sight plug holes with the car sitting still running, but if you shake the car from the fender or something, a bit will splash out.

 

I really appreiciate the quick response. I did some checking and my carb is a Holley 4150, 600cfm. Could the float just gotton out of adjustment? Can this happen, or do you think that the needle valve is dirty? Thanks Again!

 

They rarely change, but it's worth a try

4150 is the "model" number, it describes a type of carb, not a specific one. What is the list #? (front of choke tower driver's side, probably something like 1850-3) That's the specific carb part #.

 

These float adjustments don't get out of adjustment by themselves. Some possible causes for it to start flooding are:
Dirt stuck in the needle and seat assembly. Fuel filter

Dirt has got stuck in the regulator or fuel pump causing abnormal high pressure.
the Viton (rubber) needle has gone hard and won't seal (age)
the float is absorbing fuel and sinking

You have to clean out and or replace the defective part.

 

I had the same problem with my holley 600 on my old Oldsmobile Cutlass.

often after a large stab of throttle the idle would fall through the floor and the car would black smoke.

what was happening was dirt was being sucked through the glass / mesh filter i was using and jamming the needle and seat open. fuel was then flowing through the overflow and dripping into the carb. it is a weak spot on the holley, they are especialy prone to it.

two fixes, fit a paper element type fuel filter (and clean out the float bowls)

get rid of the holley and fit an edlebrock carb