Leaky B carb

[Sparky]

I have a Zenith B that runs well, but the last time I ran it I noticed some seepage of gas that seemed to be coming from the GAV driver housing area where it enters the casting (see red arrow). The Zenith A drive housing has a hex there so you can remove the housing but the B carb does not. Is the housing removable?

[Joe K]

The housing is removable, but you gotta take "steps."

It's a turned brass piece, made so that it's "pressed" into the housing.

The interference fit part where it's pressed has three "ribs" which are the majority interference.

You can pull this by threading a rod with the same thread used on the GAV needle. I can't remember but this may be 5/16-28? Which is a special thread?

Anyway, using this with a sliding weight dent remover/puller, you can quickly pull this clear.

(Heh, I used the unfluted end of a twist drill and filled the entire upper portion of the bushing with the shank - and then grabbed the outside of the bushing without crushing it using a pair of vise-grips. I then beat on the vise-grip with a hammer. Even so, it more or less made the GAV housing unusable.)

Once removed you might try sealing it with Permatex No 2. Or do as I did and use the lathe to turn another (the act of setting/pulling tends to burnish over those three "ribs") and put this new one in with Permatex.

It's really a simpler design than the Model A Zenith. And don't forget there is a spring and washer underneath the GAV bushing (this to prevent movement of the GAV through vibration - the spring and washer provide enough resistance to make the GAV moveable only by use of the hand knob - this the same action that the "fingers" on the Model A GAV housing provides.)

Vince has a pix of the inside guts of the Model B carb at http://www.fordgarage.com/pages/bcarbassembly.htm The spring and washer can be seen - but it's a little muddy.

Hope this helps. Take pix of it after you pull it. I've had others ask me what the GAV housing looks like and it would be nice to have something to refer to later.

Joe K

[Sparky]

Thanks, it sounds more complicated than I expected. I think I'll live with it for now since it isn't a large leak.

[Chuck Sea/Tac]

Is it coming up the threads?

[Sparky]

Originally Posted by Chuck Sea/Tac

Is it coming up the threads?

That's what I was assuming but on the B carb the GAV housing is a press fit, not threaded.

[Joe K]

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He may mean the threads of the GAV needle itself (that 5/16-28 whatever pointy thingy)

This shouldn't be a problem as the height of the GAV Bushing is made so that it's upper surface is above the level of the gasoline in the carburetor bowl - not to say that some sloshing around of the bowl may occur and be translated to the GAV area. Like when going up a LOONG hill.

Other carbs have attempted a solution to this. The Marvel-Schebler/Allstate carbs - some of them - have a fiber seal for the GAV needle. But not all of them. And their GAV housing is shorter.

Joe K

[Sparky]

Oh right, I didn't think of that.