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Old 09-26-2019, 07:06 PM   #1
History
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Default (GAV) Not working??

Car starts right up and idles well at very low rpms with gav open or closed.

Here's what I've noticed in the past few weeks,,,. I haven't driven it yet on the hiway but I have driven it around my shop and another area close by. I haven't really had it in third gear to speak of but it pulls fine and lugs well. Brakes seem to work well but I haven't been at high speeds yet. I kept noticing gas smell when I went into my shop and had a leak in the gas line inside the car (1930). Fixed that and kept smelling gas. I finally saw that it was seeping at the gasket of the zenith carb halves. I tightened that up and it seemed ok for a day or so, then I noticed gas dripping off the bottom bolts on the zenith.

I turn the gas off inside the car and let it idle until it dies. I choked it to make sure I emptied the carb and it keeps running so I'm assuming the shutoff valve inside car is leaking. So I either have a leaky valve in the carburetor or the float is set too high? Looks as though I need to lap the shutoff valve also to get it to shut off completely.

While running it changes nothing when I turn the (gav) valve either off or wide open. What does this say or mean? Like I said it runs fine best I can tell. Instant throttle when I mash the pedal with no hesitation.

What do you pros think??.
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Old 09-26-2019, 07:37 PM   #2
Marshall V. Daut
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Default Re: (GAV) Not working??

Check your private messages on this website.
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Old 09-26-2019, 08:05 PM   #3
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Default Re: (GAV) Not working??

Interesting question which I sure would have been shared with all!
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Old 09-26-2019, 09:26 PM   #4
Mike Peters
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Default Re: (GAV) Not working??

https://www.santaanitaas.org/tom-endys-tech-articles/

Look up Tom Endy's article on cleaning internal Zenith passageways with a paper clip. Your GAV doesn't seem to respond to adjustments.
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Old 09-27-2019, 06:49 AM   #5
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Default Re: (GAV) Not working??

Thanks but it was open when I did the rebuild. I guess something could have gotten in it but at the time was definitely open.


Had another person message me the same,,,,, I've never been wrong before (ever) this may be the first time. . Should air flow super easy through this passage or should I hear/feel some resistance if I can blow with my mouth. (I can't remember if I could even get my mouth on it) looks like I have more learning to do.

Thanks for replies.

Last edited by History; 09-27-2019 at 06:59 AM.
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Old 09-27-2019, 07:55 AM   #6
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Default Re: (GAV) Not working??

GAV stand for ???
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Old 09-27-2019, 08:10 AM   #7
jhowes
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Default Re: (GAV) Not working??

GAV=gas adjusting valve. The knob on the passenger side under the dash with the rod going to the carb. Jack
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Old 09-27-2019, 08:19 AM   #8
midgetracer
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Default Re: (GAV) Not working??

Could driver on the GAV have broken and is not actually turning the GAV valve. I have had one that the inside of the driver was not connected solidly to the half round part and was slipping. Some new ones are pinned to make this problem less possible.
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Old 09-27-2019, 08:22 AM   #9
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Default Re: (GAV) Not working??

The GAV is a lower to medium speed mixture adjustment to augment the main metering jet. It should be adjusted while driving the car for best performance at road speeds. The idle mixture screw is on top front of the Zenith type carbs. It should be adjusted for best idle.

This is a good site: http://modelabasics.com/carb%20basics%202.htm
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Old 09-27-2019, 11:15 AM   #10
Russ/40
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Default Re: (GAV) Not working??

I had the same complaint on my truck. Thankfully a mature A owner informed me that the Gav will not have any effect until Tom's get higher and fuel demand increases.

If I'm wrong, someone please correct me.
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Old 09-27-2019, 12:05 PM   #11
Tom Endy
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Default Re: (GAV) Not working??

If the comp jet (the one screwed into the fuel reservoir) is drilled out to the same size (or larger) than the cap jet, the GAV control will then have no affect because it will be the same as having the GAV wide open.

The early Zeniths have a brass GAV valve seat at the base, Ford did away with these in the later cars in favor of a cast seat because if you screw the GAV closed the brass valve could seize in the seat, then when you opened the GAV the seat would unscrew instead of opening the valve. Remove the GAV assembly and shine a light down into the tunnel to see which you have. If there is a brass seat there make sure it is screwed in tight in the casting

There could also be crud plugging either the cap jet or the comp jet. Blow all the jets out with compressed air or take them out and soak them in lacquer thinner.

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Old 09-27-2019, 01:12 PM   #12
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Default Re: (GAV) Not working??

Ok here’s what I found based on a message a very smart fellow sent me, I’ll let him take credit if he wants It. I’ll leave him anonymous. I didn’t understand that there were actually two passages under the gav body, one directly beneath it that goes to the bowl and another above that goes laterally that’s under the plug. That’s what I was so confident that the passage was open. I was able to get a paper clip through the passage under the plug and removed the cap jet and saw it exit the passage along with a wad of crud. Got it all back together and a quarter turn now gives very different results. It ran great as it was but I may be able to do more fine tuning now. No brass seat under gav needle.

Since I didn’t know that passage was there I feel like technically Ive still never (ever) been wrong.


Thanks everyone for taking the time to reply.
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Old 09-28-2019, 10:18 AM   #13
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Default Re: (GAV) Not working??

I'm sure my description was confusing to some as I'm not that articulate and even confuse myself trying to read it .

The gas adjustment valve screws into the right side of the carburetor, the choke rod attaches to it and when turned moves the gav needle in or out depending which way you turn it. I thought the only passage was where the needle goes in the bottom of the hole where the entire gav assembly goes. I could not see the other passage with light down the hole at all. But looking at the brass plug in the side of the carb I could tell where it was. I removed the cap jet and sure enough when the paper clip finally went into the passage and exited into the cap jet I could see the blockage pushed out.

I hope this makes sense enough to help someone else as this stuff isn't that hard if/once you understand it. It's easy to make a mistake though as I was confident I'd conquered the carb .
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