drrigg

I am in the neverending process of making the wife's '64 coupe a reliable runner but this leaking carb is driving me BATTY! I've done a full rebuild using reputable parts and the engine starts beautifully when cold and runs strong but is very reluctant to hot start and drips gas after shut down. I've adjusted the floats a number of times and even set them to close the valves slightly early (1/2" between float and gasket as opposed to 7/16" indicated in manual) but the leak persists. The secondary has about 1/4" of fuel standing in them and the manifold has puddles inside. I have come to the conclusion that the fuel pump is over pressurizing the system and I'm thinking of installing a regulator but can find no real specs for the fuel needs of the Carter AFB. I find many people speculating on what the maximum pressure should be but can find no reference to what the minimum pressure might be. Ideas?

Frankie the Fink

The sweet spot for both WCFB and AFB carbs is 4-1/2lb to 5-1/2 lbs....they can take a bit more but not much... It sounds like you have classic percolation. Shoot the fuel bowls 20 minutes after a hot run with an I/R temp gun..anything north of 145* or so is a problem...

vettepoor

I agree with the Percolation thought, as you said this occurred after a run. If fuel pressure was too high, you would probably see issue at idle. My fuel pump delivers close to 6 1/2 lbs pressure and I'm running dual WCFBs with no problem. Search the forum, there is a lot of info on this issue.

Plasticman

Just a note on fuel pressure. I was talking to a long time carb rebuilder recently, and he stated that owner's fuel pumps were increasing in pressure due to corn (ethanol) laced fuel attacking the fuel pump "rubber" valves.............new one on me, but thought I would put it out there.

And I agree that the OP's issue sounds like percolation. Very familiar with it on my dual AFBs. Do a search with that as the topic.

Plasticman

tbarb

Double check your float setting, the 1963 shop manual lists float level at 7/32 from top of float to gasket surface. I would lower it and check the gaskets around the needle and seat assembly where they screw to the carburetor top. Have you checked the floats for weight?

Fuel pressure should be approx. 5-6psi with a stock pump. Fuel pressure is a function of the spring above the diaphragm.

olescarb

I agree with the fuel percolation thought, if the manifold has exhaust heating the base plate and a steel plate above the base gasket I would recommend installing an 1/4" allen head pipe plug in the 2 exhaust passages to block the exhaust from overheating the carb.
I hope this helps Henry @ oles carb

plaidside

I believe the spring is what determines the pressure the pump produces.
Joe

GTOguy

The movement of the diaphragm provides the pressure. If the diaphragm were degraded from alcohol in the fuel, the pressure would drop, not increase. Rotted rubber is less elastic and firm. So, less pressure.

Plasticman

I completely understand that, but he was saying the valve seals stick, causing the pressure to increase, before the valves open............I am just repeating what he said, since I never have seen it.

Plasticman