GAV Question ?

[Lefthander1930]

How muck should the GAV open ? Using a clock 12 o'clock being close How much should it open ? Mine only opens to about 90 degrees or 12 to 9. I this about right ? Don't want to force it.

[WHN]

You should be able to open multiple turns. I start our car by opening one full turn. Once car is running, I close to about quarter turn open.

[Ruth]

There should be no restriction in turning it CCW. But you should not need to turn it too far open.

[jquinlan]

First thing you need to do is gently close your GAV all the way. Turn it clockwise. But very gently so you don't tighten it and harm the needle tip on the end of the GAV. Once it's closed turn it left 90 degrees. This is usually a good starting point to get your car running. If it's cold outside, then open it up (left) a little more until the car warms up and then put it back to a quarter.

Depending on your carb, your GAV may need to be opened more or less. Many carbs have incorrectly sized jets which still allows the car to run but may need GAV adjusting to lean or enrich the mixture.

12:00 position is irrelevant as the closed position on all carbs are different.

[jayvee34]

Most are different. Mine opens to start @ 1 O'clock, after warm up, about an eight of a turn counter clockwise. IMO, 3/4 turn clockwise is a little much, but if it runs and performs
good, O.K.

I'm using your 12 O'clock analogy.

[Ruth]

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Originally Posted by jayvee34

Most are different. Mine opens to start @ 1 O'clock, after warm up, about an eight of a turn counter clockwise. IMO, 3/4 turn clockwise is a little much, but if it runs and performs
good, O.K.

I'm using your 12 O'clock analogy.

When your engine warms up you open it more? Usually they are turned CW after warmup.

I guess you said it "Most are different."

[redmodelt]

My analogy is; they are not clocked so you have to close as above and open/close x-amount as needed.

[jayvee34]

Originally Posted by Ruth

When your engine warms up you open it more? Usually they are turned CW after warmup.

I guess you said it "Most are different."

Sorry, I should have said clockwise I guess that 12 0'clock thru me off.
Actually I open it about an 1/8 of a turn to start and warm up. Then back a
little. Thanks for correcting me.

[Curtis in MA]

The question was how far should it unscrew. That would be all the way out of the housing.

[ETAModel]

I know the 30 Fordor I drive the GAV will open over one complete turn. I haven't tried to remove it.
When first starting i turn the GAV 1 turn ccw from bottom, then after she warms up move to 1/4 turn.
Reading the service bulletins I see where it says for maximum efficiency close the GAV. Not sure if she'll run with the GAV close and may try it on the next outing.

[jquinlan]

You have to keep in mind the GAV's main purpose is to give the driver a mechanism to fine tune the car's performance by enriching the mixture. According to Steve Pargeter's book, the zenith carbs were designed to run a little lean to allow them to run at high altitudes. The GAV gives the operator a chance to enrichen the mixture somewhat at lower altitudes and also during cold weather. So adjust the GAV to do what works well for your carburetor, even if it means closing the GAV most of the way.

I just finished rebuilding a carburetor for a friend. Jets correctly sized and flow tested correctly but the GAV needs to be almost closed for optimal performance. I checked and rechecked this carb thinking I missed something but an almost closed GAV is what needs to happen for this particular carburetor.

I've met a few people with carbs that run the best with the GAV almost closed. Almost closed is ok but if you have to open the GAV a lot more than a quarter probably means you might have other issues with the carburetor that need to be addressed (something is clogged possibly).

[Ed in Maine]

Hello jquihlan, would you happen to know what the flow (in ml/min) was through the Compensator and the Main Jets for this carburetor? I rebuild carburetors for my fellow club members and I am always looking at flow data that provides the best results. Usually your situation is the result of a Main Jet set at the high end of its range. Thanks, Ed

[Bob Bidonde]

This should help. It is important that when adjusting the carburetor's idle air screw, the GAV should be 1/8 turn open.

[Lefthander1930]

Curtis in MA said it right. How far should the GAV unscrew. With that said my GAV only unscrew about 1/4 turn without binding. What would cause it to bind up & what damage will I do unbind to remove & inspect ?

[jquinlan]

Originally Posted by Ed in Maine

Hello jquihlan, would you happen to know what the flow (in ml/min) was through the Compensator and the Main Jets for this carburetor? I rebuild carburetors for my fellow club members and I am always looking at flow data that provides the best results. Usually your situation is the result of a Main Jet set at the high end of its range. Thanks, Ed

Ed, the main was flow tested at 145 and the compensator was 150. What flow ranges do you use when sizing your jets? There are different flow recommendations out there (Fords, Chris Pelikan, Al Blatter, Tom Endy, Steve Pargeter, Howard Taylor or Larry Brumfield). Also, I sent you a pm last week with a question about your stainless wire technique.

Thanks

[nkaminar]

Left, Take the adjustment rod off by pulling up on the sleeve against the spring and unhooking the rod. Take the sleeve and spring off and set them aside. Push the adjustment rod up to hook it on the hole through the firewall so that it is out of the way. Unscrew the housing for the GAV needle and examine it to see what could be restricting the needle from moving more than 1/4 turn. There are four segments at the end of the housing with a steel ring around them to help hold the needle in position. There may be something fishy there. You can take the steel ring off to see if that will help.

[Patrick L.]

Originally Posted by nkaminar

Left, Take the adjustment rod off by pulling up on the sleeve against the spring and unhooking the rod. Take the sleeve and spring off and set them aside. Push the adjustment rod up to hook it on the hole through the firewall so that it is out of the way. Unscrew the housing for the GAV needle and examine it to see what could be restricting the needle from moving more than 1/4 turn. There are four segments at the end of the housing with a steel ring around them to help hold the needle in position. There may be something fishy there. You can take the steel ring off to see if that will help.

Yep

[Lefthander1930]

Took the GAV apart & notice the sleeve was split at both ends. Looks like the sleeve was home made.Got a new sleeve from Vintage Ford. Put it back together and now I have full opening as needed if needed. Thanks all for the info and help.

[Patrick L.]

Good.