The Ford Barn - View Single Post - How do I stop the brass GAV housing gasoline leak at carburetor?

Jazzjr · 01-19-2013, 10:45 PM

Possible Gas Adjusting Valve Seat is Blocked with dirt or rust.
Gas Adjusting Valve is open too much or seat is not honed to let needle seal.
Zenith Carbs before 1929 had a removable Brass seat, all others after 1929 had the seat cast into the Housing. I have stopped one that was leaking using the Procedure below. You also need to run a tap, to clean out the threads for the housing, it may not be inserted enough. Gas Adjusting Valve (GAV) hole, in lower casting, has 1/8-27 NPT (Pipe) threads. Use caution not to cut threads deeper, as it is a pipe thread.

Gas Adjusting Valve Seat Honing Tool & Guide

To obtain a good seat when Gas adjusting valve is closed, the seat sometimes needs to be polished to remove pits, dirt scratches, etc. This tool and guide provides a mating, aligned surface that can be spun against the seat with polishing compound on it. The tool is made by soldering two needles together back to back. The end that will go into the guide and provide the polishing surface needs to have its threads removed to enable it to be spun continuously with a drill. Using an old GAV housing, I've removed the spring to let the tool spin more freely. Some people also cut down both ends of the housing.

I borrowed the above from http://www.model-a.org/

01-19-2013, 10:45 PM	#7
Jazzjr Senior Member Join Date: May 2010 Location: Crown Point, NY and Punta Gorda, FL. Posts: 259	Re: How do I stop the brass GAV housing gasoline leak at carburetor? Possible Gas Adjusting Valve Seat is Blocked with dirt or rust. Gas Adjusting Valve is open too much or seat is not honed to let needle seal. Zenith Carbs before 1929 had a removable Brass seat, all others after 1929 had the seat cast into the Housing. I have stopped one that was leaking using the Procedure below. You also need to run a tap, to clean out the threads for the housing, it may not be inserted enough. Gas Adjusting Valve (GAV) hole, in lower casting, has 1/8-27 NPT (Pipe) threads. Use caution not to cut threads deeper, as it is a pipe thread. Gas Adjusting Valve Seat Honing Tool & Guide To obtain a good seat when Gas adjusting valve is closed, the seat sometimes needs to be polished to remove pits, dirt scratches, etc. This tool and guide provides a mating, aligned surface that can be spun against the seat with polishing compound on it. The tool is made by soldering two needles together back to back. The end that will go into the guide and provide the polishing surface needs to have its threads removed to enable it to be spun continuously with a drill. Using an old GAV housing, I've removed the spring to let the tool spin more freely. Some people also cut down both ends of the housing. I borrowed the above from http://www.model-a.org/ Last edited by Jazzjr; 01-19-2013 at 10:58 PM.