C2 Holly Carb Leaking

[Gary D.]

I just rebuild a Holly carb off a 65 327/365hp that was leaking fuel when shut off. The gaskets were also leaking. I replaced the secondary diaphragm, needle & seats, both floats, pump diaphragm, power valve, all gaskets and seals. I have reset the float levels, and done the normal adjustments. I still leak fuel into the throttle body after the engine is shut off. Any one have any Ideas????
Thank You Gary

[Mark B.]

Re: C2 Holly Carb Leaking

Gary,

A couple of things you might look into. I believe that the carb used is a 4160 rather than a 4150 with a secondary metering block. If so, I would check the clutch head screws on the secondary metering plate to make sure that they are all tight. Next, I would look at the power valve and make sure that the gasket is properly positioned and snug between the valve and the primary metering block. If those appear to be OK, then I would look again at my float levels. With the engine idling, the fuel should just "seep" out the vision hole in the side of the float bowls. I always set my secondary floats somewhat lean so that the fuel does not even seep out. With that out of the way, try installing a thick carb base gasket between the manifold and the carb to decrease the amount of heat conducted betweent the two assemblies. During hot soak when the engine is turned off, the carb gets very hot and fuel can boil in the float bowls and be forced into the engine thru passages in the carb. A sheetmetal heat shield under the carb may also be in order. Good luck.

[Gene M.]

Re: Holley Leaking.......must be warped

Check that all the mating surfaces are flat. A warped casting is the primary cause of leaks........

[John H.]

Re: Holley Leaking.......must be warped

A thorough rebuild of a 40-year-old Holley should include checking and milling the main body surfaces dead flat and checking the metering block(s) for flatness as well. New gaskets won't seal a Holley with a warped main body or metering blocks.

[Clem Z.]

do not let anyone

mill the metering bodies to make them straight,they must be straighten in a fixture using a arbor press. when you mill the metering bodies flat you remove the little cast in projections the make the seal around the gasket openings