Barry Grant 625 Road Demon Carb

I don't know if anyone has dealt with this but I'll ask anyway. I have a 625 BG road demon carb. It leaks down after shut-off. I've tried new gaskets, power valve, cleaning all air bleeds but no luck. Any ideas? Perhaps send it back to h*ll!

 

is it boiling the gas out of the bowls?
does it only leak down when you turn off the motor when its hot, or does it do it if you just ran the motor for a minute and shut it off?

 

Bryant, I wondered about the heat also. It bleeds down under both conditions. I've read about this before but nobody provides a solution.

 

I am no expert.. Just wondering where the fuel is going. Does it go into the engine or is it going back into the fuel system?

 

i wonder the similar thing.
is it hard to restart the motor after the bowls have drained? is it flooding the motor?

i would check the float levels. if they are good then i would try lowering them 1/2 a turn and if that doenst do it try another 1/2 turn.

it could be that the angle of the carb is letting the fuel level be just a little to high on the metering block allowing it to drip out.

the other thing is if some how one of the circuits in the carb is working like a siphon effect drawing the fuel out of the bowls. the only one that i can think of is the accelerator pump but i can see how it would create a siphon.

 

I also wonder how it was determined that it bleeds down..

 

The fuel level in the bowl drops slowly over several hours as seen through the site glass. It leaks into the intake, not a good thing. Trouble shooting guide says, gaskets, power valves and air bleeds. Nothing about the accelerator pump. The float level is fine. And, it continues to leak down past the site glass! Not sure what to try next.

 

Pluged bowl vent?

 

a bad power valve or its gasket would defiantly behave like that. i totally blanked out on the power valve. with the alcohol in todays fuels alot of the older power valves and other rubber components slowly get eaten away.
have you tried replacing the power valve?

 

Bryant, tried all of that!

 

What kind of fuel pump?

 

i would have to guess the metering block has a porosity problem. ive head of these problems before. it requires a new metering block. the only way i can think of checking is to take off the metering block and see if the chamber where the power valve gets it vacuum signal from is wet from the gas leaking in to it or if its dry.
thats the only place that i can think of that the gas could leak to and get into the intake manifold. every thing else goes up and above the float level in the bowls.

 

Good point and that's exactly what I was going to add too. Even Holleys have issues with that on ocassion.

 

Thanks for the responses. I was concerned about the metering block!! I'm trying one more thing. I filled the bowls as usual and removed the carb. It is sitting in a container and we'll see if it leaks down when removed from the car.

Dave B, it is a holley blue, not my first choice!

 

I thought the blue was for higher pressures. I understand a red is for carbs.. But there are some applications like NOS that need the higher pressures I think.. I am assuming you have a regulator.