GAV closing

[Phred]

My GAV on the Zenith carb will not stay at 1/4 to 1/2 turn open, but will self close while the engine is running. It does run better at 1/4 - 1/2 turn open.

What can I do to have the GAV stay in position without affecting the in/out operation of the choking operation.

As always,
Thanks in advance

[Joe K]

Your GAV is held in place from moving by the three or four "fingers" on the bottom of the GAV bushing/housing.

With a small wrench you can remove the GAV bushing/housing and take a look at the condition in there.

Remove your GAV adjustment rod by pulling back on the spring/sleeve and disconnecting the rod from your GAV needle. Unscrew/remove the GAV needle. THEN you can unscrew the GAV housing/bushing with a small open end wrench.

Inspect the three/four fingers - you may have one broken out (common) or you may be missing the little "circlip" spring that fits in the groove at the tips of the fingers. (common and frequently done to allow the GAV needle to be more easily adjusted.)

This is how it is supposed to work. The three/four fingers present "rubbing resistance" against the GAV needle and prevent it from moving by vibration. Restorers sometimes have problems getting the proper amount of tension here: either the GAV needle turns too hard, or like you it turns too easy.

All you need to is find a way to increase tension between the GAV needle and the housing. A new needle may do the trick by itself. Or you may want to try a new GAV housing/bushing.

Take a look. It's not a hard fix once you understand what the fingers do and how they and the circlip work to keep the GAV needle from moving.

Heh. Usually the GAV needle is too tight. You can use an ice-pick to "open up" the fingers and stretch the circlip - but someone seems to have already done this?

You just need a "negative ice-pick?"

Joe K

[fredski]

I would just change the rubber gromlet going through the fire wall and the
gav rod will grip tighter.

fredski

[jmeckel]

Does your choke rod / GAV adjustment rod have the spring and washers like original? If not order them. My A came with out them, someone had used a piece of copper pipe to hold the rod to the GAV driver, and the GAV would move all over, replaced the pipe with the proper parts problem solved.

[Hoogah]

How much total rotation is there supposed to be for the GAV rod? Mine rotates no more than a quarter turn in total, so I can't really follow the recommended adjustment procedure for starting and driving. I wonder what I'm missing or have out of adjustment at the carby end?

[Tom Wesenberg]

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Actually you should be able to keep turning CCW until the needle comes all the way out of the carb.

[Joe K]

Originally Posted by Hoogah

How much total rotation is there supposed to be for the GAV rod? Mine rotates no more than a quarter turn in total, so I can't really follow the recommended adjustment procedure for starting and driving. I wonder what I'm missing or have out of adjustment at the carby end?

You don't say your carb, but if it is a Model B carb you could very well have the problem.

The orientation of the Model B carb is a little "different" compared to the Model A carb. IIRC, the flange on the B was made to mate to the flange on the B intake - which is a little "tilted" or turned compared to the same place on the Model A. When one mates a Model A intake with a Model B carb, the mismatch is enough to cause the GAV driver rod/sleeve/spring to be hard to make the connection - and when made - hard to turn.

Another possibility for the problem is some of the repop rubber grommets on the standoff under the gas tank are a bit "oversized" resulting in additional friction here. Someone above mentioned this as a possible solution to too loose a GAV adjustment. A tapered reamer can open up the inside of the grommet and relieve the friction. A little soap helps too.

Hope this helps. As Tom says, you should be able to TOTALLY unscrew the GAV using the adjusting rod.

Joe K

[nosbod]

Originally Posted by Tom Wesenberg

Actually you should be able to keep turning CCW until the needle comes all the way out of the carb.

Not if its right hand drive !

[darrylkmc]

Originally Posted by Joe K

You don't say your carb, but if it is a Model B carb you could very well have the problem.

The orientation of the Model B carb is a little "different" compared to the Model A carb. IIRC, the flange on the B was made to mate to the flange on the B intake - which is a little "tilted" or turned compared to the same place on the Model A. When one mates a Model A intake with a Model B carb......

Joe K

The carb orientation is the same for the Model A or Model B Carburetor, it is the Model B Intake Manifold that has a different angle, this is the reason that some people will enlarge the inside of a Model A Intake Manifold to match the opening size of the Model B Carb.

Darryl in Fairbanks

[Joe K]

Originally Posted by darrylkmc

The carb orientation is the same for the Model A or Model B Carburetor, it is the Model B Intake Manifold that has a different angle, this is the reason that some people will enlarge the inside of a Model A Intake Manifold to match the opening size of the Model B Carb.

Darryl in Fairbanks

Thank you for that clarification. Vince Falter discusses the differences between the manifolds at http://www.fordgarage.com/pages/Bintakevariation.htm

Joe K