Holley 4180 Troubleshooting

I have a Holly 4180 carb that has had a leak at the accelerator pump area. I ordered a diaphragm from you(Appreciate the fast service) and it still leaks. Is the cover that sensitive to leaks? I don’t see any cracks or such. Appreciate help and if a replacement cover will correct.

The cover gets warped. Sandwich the cover in a vice and apply some heat to it. Tighten the vice a bit so that it becomes flat. Allow to cool.

You can also file a bit at each corner where the screw goes in. It will be high there.


Most likely the choke isn’t adjusted correctly. See this page.


Flooding is when there is too much gas in the float bowl and it is running out of the top, or down the carburetor and out of the throttle shaft.

Some causes:

  • The number one cause is leaky needle & seats.
    • Dirt may have gotten into the seat. Not unusual after rebuilding the carburetor.
    • Needle damaged by putting pressure on it. Happens when adjusting the float.
    • If the gas has been sitting for a prolonged period the gas may have varnished the inside of the carburetor.
  • The float might be leaking.
    • Shake the float and listen for gas inside.
    • Heat up a pan of water just prior to boiling. Immerse the float and look for bubbles as the air inside the float heats up and expands.
  • Test the fuel pump. Refer to the owners manual for proper pressure, but should be 5-7 lbs. New fuel pump are especially troublesome.
    • If not sure you can add a pressure regulator between the fuel pump and the carburetor.
  • Check floats for any binding.
Updated on 12/20/2020

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