The Ford Barn

fiftychev · 12-12-2015, 11:10 PM

I have a Marvel Carb on a 30 Model A. It leaks where the GAV rod goes into the carb. I took the gas line off the carb and it continued to leak for a while.

The disconnected gas line leaks a couple of drops an hour so I guess the shut off valve isn't totally shutting off the gas.

What might be the problem with the carb?

Is the slight internal leak of the shut off valve a problem?

Mike V. Florida · 12-12-2015, 11:36 PM

There is a valve that the float operates. This should shut off the gas getting into the carb regardless of the condition of the valve in the car.

The valve in the car does need attention. Could be as simple as lapping the brass surfaces.

fiftychev · 12-13-2015, 12:09 PM

Thanks Mike
Regarding the carb, could that mean that the float is set wrong?

duke36 · 12-13-2015, 02:48 PM

If understood correctly, the leak is coming from the GAV ? I had the same problem.There is a rubber (or leather?) washer near the GAV brass tip you may want to check if seated properly. Also, I added a thin washer and tiny amount of teflon sealant where the outer portion screws in to the carb body . That stopped that leak. A leak from the air horn was coming from the float valve. Placed a dressed brass needle in which helped. As added insurance, add a modern small 1/8" ball valve available from most hardware stores to the gas line. There is a great thread on this site for Marvel rebuild but can't place the author.

glenn in camino · 12-13-2015, 09:00 PM

Make a way to hang a plastic bucket under your carburetor when you're car is stored in your garage.

JamesAC · 12-13-2015, 09:31 PM

Sponsored Links (Register now to hide all advertisements)

I just replaced the under tank valve in my 1930 model because even with it shut off, it allowed enough fuel to pass through it to fill the carburetor and even though there was no drip from the carburetor (new Tillitson) there were lots of gas fumes coming from it. New under tank valve fixed the problem.

@ fiftychev: So you have a 1950 Chevy? I have a 1950 Plymouth.

fiftychev · 12-13-2015, 10:30 PM

Yup I have a 50 Chevy Coupe and a 50 Chev Ute. The Model A belongs to my daughter.

fiftychev · 12-13-2015, 10:34 PM

Thanks rip94611. I have taken what I would call the needle part of the GAV out of the carb. ITs very tapered and looks pretty good . Is the rubber or leather seal in the seat part?

12-12-2015, 11:10 PM	#1
fiftychev Junior Member Join Date: Oct 2012 Posts: 23	Gas Leak I have a Marvel Carb on a 30 Model A. It leaks where the GAV rod goes into the carb. I took the gas line off the carb and it continued to leak for a while. The disconnected gas line leaks a couple of drops an hour so I guess the shut off valve isn't totally shutting off the gas. What might be the problem with the carb? Is the slight internal leak of the shut off valve a problem?

12-12-2015, 11:36 PM	#2
Mike V. Florida Senior Member Join Date: May 2010 Location: Florida between Sarasota and TampaSouth Florida Posts: 14,054	Re: Gas Leak There is a valve that the float operates. This should shut off the gas getting into the carb regardless of the condition of the valve in the car. The valve in the car does need attention. Could be as simple as lapping the brass surfaces. __________________ What's right about America is that although we have a mess of problems, we have great capacity - intellect and resources - to do some thing about them. - Henry Ford II

12-13-2015, 12:09 PM	#3
fiftychev Junior Member Join Date: Oct 2012 Posts: 23	Re: Gas Leak Thanks Mike Regarding the carb, could that mean that the float is set wrong?

12-13-2015, 02:48 PM	#4
duke36 Senior Member Join Date: Jun 2015 Posts: 1,425	Re: Gas Leak If understood correctly, the leak is coming from the GAV ? I had the same problem.There is a rubber (or leather?) washer near the GAV brass tip you may want to check if seated properly. Also, I added a thin washer and tiny amount of teflon sealant where the outer portion screws in to the carb body . That stopped that leak. A leak from the air horn was coming from the float valve. Placed a dressed brass needle in which helped. As added insurance, add a modern small 1/8" ball valve available from most hardware stores to the gas line. There is a great thread on this site for Marvel rebuild but can't place the author.

12-13-2015, 09:00 PM	#5
glenn in camino Senior Member Join Date: May 2010 Location: Camino, CA. Posts: 3,086	Re: Gas Leak Make a way to hang a plastic bucket under your carburetor when you're car is stored in your garage.

12-13-2015, 09:31 PM	#6
JamesAC Junior Member Join Date: Nov 2015 Posts: 26	Re: Gas Leak Sponsored Links (Register now to hide all advertisements) I just replaced the under tank valve in my 1930 model because even with it shut off, it allowed enough fuel to pass through it to fill the carburetor and even though there was no drip from the carburetor (new Tillitson) there were lots of gas fumes coming from it. New under tank valve fixed the problem. @ fiftychev: So you have a 1950 Chevy? I have a 1950 Plymouth.

12-13-2015, 10:30 PM	#7
fiftychev Junior Member Join Date: Oct 2012 Posts: 23	Re: Gas Leak Yup I have a 50 Chevy Coupe and a 50 Chev Ute. The Model A belongs to my daughter.

12-13-2015, 10:34 PM	#8
fiftychev Junior Member Join Date: Oct 2012 Posts: 23	Re: Gas Leak Thanks rip94611. I have taken what I would call the needle part of the GAV out of the carb. ITs very tapered and looks pretty good . Is the rubber or leather seal in the seat part?