GAV Question

[Nabco]

Hi gentlemen, I'm a new A owner, my father-in-law gave me his 1930 Deluxe Coupe. He has been teaching me how to start it, drive it, etc. for the past 28 years knowing that some day it would be mine....finally at 90 years young he decided to pass it on.

It starts every time and runs great...however I have a question on the GAV, he always told me to turn it counter clockwise to start and move it back clockwise as the engine warms up. I've been reading the forum and it appears the travel distance on my GAV is not consistent with what I'm reading.

At full clockwise the pointer is at about 9:00, at full counter clockwise it is at 6:00, so the total travel is only about a quarter turn, is this normal, it seems like in the posts I've read there apears to be more travel...could it be the type of carburetor my father-in-law has on the car.

I'm going to call him to ask but thought I would post the question here too.

Thanks for the help.

[Joe K]

With a normal Zenith carburetor, you get any number of turns. From full closed (clockwise) to falling out on the pavement (many turns counterclockwise)

No stops. And as much GAV as you care to run.

Now that said, some have retrofitted a Model B carburetor to their Model A ford. There is frequently some mis-match/misalignment here which results in binding of the GAV connection to the carburetor. This binding may be what you're experiencing?

You should find a spring loaded (from the firewall) sleeve which can be lifted up the GAV rod to reveal the GAV needle connection between rod and carburetor. Sometimes you can play around with this (grease maybe?) which may give you more free motion before binding?

Take a look at Ebay under "Model A Ford carburetor" and you'll see pix of MANY different kinds and makes of carburetors. The Model A and Model B carbs are not marked on the bodies as such - but those of us who have been hanging around these creatures have learned how to see the difference. And all are pretty well marked on Ebay. A "reference book" of sorts.

Or you may have some other carburetor which I'm not as familiar with. There are MANY aftermarket carbs - but none that I'm aware with a limited travel of the GAV needle. (Well some aftermarket carbs use the GAV rod ONLY as choke by pulling up or turning.)

You might take a pix of your carb and upload it here if you have trouble identifying?

Joe K

[Purdy Swoft]

In cold weather, it may be necessary to open the GAV one full turn counter clockwise off the seat. Turning the gav clockwise leans the mix and all the way clockwise puts the gav needle on the seat, so to speak. Most model A carbs run best, 1/4 turn counter clockwise off the seat after a brief warm up. Model B carbs should be run with the gav closed all the way clockwise after a brief warm up. When the engine warms it will begin to lope if the gav is too far open and it will be time to turn the gav knob clockwise as needed to smooth idle speed. Some have said that the gav has no effect on idle. The thing is that most don't run on the idle circuit at start up if it actually ever runs on the idle circuit at all. The idle circuit only kicks in at very low rpm. In other words, the engine will idle without actually being on the idle circuit but will idle at a higher rpm. Usually if an engine requires over a quarter turn off the seat to run after warm up there will be a vacume leak somewhere. The pot metal aftermarket carburetors usually warp at the mounting flange and require that the gav be opened farther in the counter clockwise direction to compensate for vacume leaks.

[Nabco]

Thanks guys, I understand the concept of the GAV in that the fuel mixture is lean at fully seated and is richer the more it is turned counter clockwise (I think I have that correct).

The question is the GAV on my A only travels a quarter of a turn, at seated the pointer is at 9:00 at full rich it is at 6:00, only a quarter of a turn...Based on what I'm reading that does not sound normal.

I don't believe it is binding, as I remember this is all it always traveled....just wondering what my father-in-law may have done differently.

[Ron in Quincy]

When rebuilding the carburetor, one of the tests I do is to be sure the GAV needle is seating and actually closing off the passageway to the secondary well.

I have found many carburetors that the GAV needle is not seating.

I like to size my jets so 1/4 turn open to start the cold engine; when the engine is warm, I seat the GAV needle.

Another test I make to be sure the idle jet and compensating jet is properly sized, when the engine is warm I open the GAV needle 4 or 5 turns open to be it has no effect on idling.

The owner manual says to close off the GAV needle when normal highway driving to improve gas mileage; if left open it can reduce gas mileage 2 to 3 miles per gallon.

Ron

[Purdy Swoft]

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The pointer on the choke knob won't necessarily point at the same spot with every car A lot may depend on whether an original or aftermarket choke rod is used. Some aftermarket choke rods have a threaded on knob, the original knob isn't threaded to the choke rod. Sometimes the knob can just be loose with an aftermarket choke rod and not actually be moving the gav at all. In any case,all cars won't seat at 9 oclock . Its not where the pointer happens to point but how far off the seat that the needle actually is. The knob should take several turns to go from full lean to full rich. Hope this helps.

[Nabco]

Thanks, so the fact that my GAV only turns about 1/4 turn in total is probably not right

[kingbee]

Also, sometimes there is a quarter turn of play between the rod and the GAV needle, so you may not be moving the needle adjustment at all. A quick examination under the hood will verify what's happening. Perhaps a LITTLE more effort is needed to actually turn the needle....

[mshmodela]

Welcome to the world of Model A's as a new owner myself, you've come the the right place...

The folks here are lot of help. I had their help to learn on my own to start my car.. This along with this web site helped me a lot:

http://modelabasics.com/Starting%20&%20Driving.htm

The GAV is a needle value so just close it with little force.. then if cold, I open it one full turn CCW, pull the chock for one crank then let it in... I learned with the help of folks here not to OVER chock and flood my engine...

[Nabco]

Talked to my father-in-law, he said to just turn it, may be a little piece of "gunk" (must be a technical Model A term) in there...sure enough it's working fine now....I was just afraid I was going to break something.

Thanks guys!

[marc hildebrant]

Nabco,

If you do not have the owners manual, be sure and buy a copy from the Model A parts companies.

Your father-in-law knows the car, but its always good to check that the advice matches the Ford info.

Marc

[Nabco]

Originally Posted by marc hildebrant

Nabco,

If you do not have the owners manual, be sure and buy a copy from the Model A parts companies.

Your father-in-law knows the car, but its always good to check that the advice matches the Ford info.

Marc

Thanks Marc, planning to head out to Gaslight on Monday, very convenient about 25 miles from my house, to pick one up.

Nick

[Tony S,Fl.]

Maybe the little C clip at the end of the gav housing might be too tight. Spread it open a little or remove it for testing. Tony