73bbc

I'm working on a friend's 69 with an aftermarket Holley 600 cfm 80457. Everything is working fine, except that since the carb was new, the secondary bowl leaks fuel into the manifold after you shut it off hot.

The fuel is not dripping from the boosters, but seems to be leaking from the slots at the bottom of the venturi (transfer slots on secondaries??) This is a 4160-style carb with a metering plate on the secondary, and I'm not very familiar with the fuel circuits in these.

Here's what we have tried:
1. remove the gas cap in case pressure in gas tank is overcoming the N&S
2. Replace the secondary N&S, then the float
3. Installed a plastic spacer between carb & manifold to insulate carb from engine heat
4. general rebuild with gaskets, new N&Ss

Anybody seen this before? I'm really scratching my head here.

Brettmc

Try lowering the gas level in the bowl.

73bbc

I didn't mention that specifically, but we tried lowering the float level several times to the point where it bogged on sec opening. It didn't make it stop leaking until the float was too low to run.
I don't think it's percolating or fuel would come out of the boosters.
It seems like a mechanical defect or something, since the float level, N&S, and gaskets have been ruled out.

Tired74

Did you ever solve this problem? I have done the same as you. Mine leaked so bad over nite they hydrolocked the engine so I had to drain a couple of cylinders of fuel.

Stingray1973

I recently bought a Holly 670 Street Avenger and had a similar problem.....the rear block had a manafactures defect and hole cast into the block...when the carb filled with gas then it just leaked right out onto the manifold...lucky the freakin car did not catch fire!!!

Double check the blocks on each side and you may have a case defect with a hole. You could block with a set screw if needed. I called Holley and they sent a new block overnight for free.

Tired74

My car did catch fire. Not from the carb exclusively but the excess fuel didn't help. I have adjusted the float and cleaned the N&S and the problem is intermittant. Now I am speculating the gas tank is pressuring the the system somehow. The problem is not on the primarys and I have a hard time believing the gas tank can pressurize greater than the fuel pump itself.

I am trying to find information on the vapor separator valve right at the tank. Anyone have a description of what is in the little plastic box?

Thanks

Tired74

Found the answer in the archives. It seems seperator can be spelled several ways. Separator, seperator,seperater and so on. Neat little device.