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Old 07-31-2018, 08:04 AM   #1
Dennis D 1929
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Default Choke rod question

Please excuse my ignorance (new to Model A's) but I'd like to know what the choke rod rotation feature is all about. Does this change the rich mixture setting ? My car started running a little rough, so just for grins I rotated the knob from the 9 o'clock position to the 6 o'chock position and the car started to run better and not back fire when accelerating. What did I change ? What setting is normal ? Thanks FWI I did not change the retard lever during this experiment, it was left in the full down position.
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Old 07-31-2018, 08:21 AM   #2
Doug_Knutson
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Default Choke rod question

Sounds like you need to learn the fine details of running a Model A .. That rod is directly connected via the carb via a screw & jet to the main gas jet & the choke lever. You should turn it in fully (turning right) if your engine is running it will likely stumble and might stall. That is the min or leanest position. Most Model A operate best open roughly between 1/2 a turn to 1-1/4 open (CCW) .. but if the carb was not built correctly or plugged the adjustments might be different. If the engine is operated too lean it will run hot and back fire and be lacking power. The timing lever ,, again depends if it was setup correctly but you should NOT be running full advance unless the engine is up to full RPM .. You might be damaging your rod and main bearings prematurely.


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Old 07-31-2018, 08:22 AM   #3
SeaSlugs
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Default Re: Choke rod question

I would highly suggest purchasing the repo owners manual. Explains when and how to set all the controls.

What your turning is called the GAV (Gas adjustment valve i think it stands for) on really cold days or dragging up a long steep hill you may have to open it a bit more to introduce a bit more fuel.

Always always always start the model A with the retard lever fully up, once it starts bring it about 1/4-1/2 way down. Around town 1/2 is good, highway cruising bring the lever nearly fully down. Might have to back it off a bit going up steep hills as you slow down.
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Old 07-31-2018, 08:24 AM   #4
Al 29Tudor
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Default Re: Choke rod question

Dennis,
You got it right. That is the GAV, "Gas Adjust Valve" and it does just what you discovered it enrichens the fuel mixture. Mostly you need it in cold weather when starting and while the engine is warming up. There is no fixed position as it different for every car but usually is opened about a quarter turn from closed.
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Old 07-31-2018, 08:48 AM   #5
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Default Re: Choke rod question

There are a lot of Model A Ford starting procedures on the Web and how to set up the GAV you are questioning. I would suggest googling on "Model A Ford starting procedure" and a bunch will pop up! Pick any one! most are the same except for a few words! Or google on Model A Ford GAV and bunch more will pop up!
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Old 07-31-2018, 09:26 AM   #6
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Default Re: Choke rod question And how to use GAV and choke on startup

Dennis,

This is what I have learned about using the GAV since 1962.

Every carburetor is different. Some are setup CLOSE to Ford specs. Many are not so this is only a guide and should get you up and running.

As mentioned above: Some run well at 1/4 turn others need more GAV...

Benson's posting from last week.

07-28-2018, 05:41 AM #9
Benson


This is written for a stock Zenith carburetor.


Improper use of the choke will flood the engine with unburned gasoline.

The manual choke on this engine does not work the same as one on a 40s to 80s engine.

Choke should not be closed more than ONE SECOND at a time while turning engine over.

Any more than ONE SECOND will flood engine.

GAV should be open 1/4 turn (OR whatever setting that you find works for your engine) at all times when starting or driving.

If engine starts and dies then open the gas adjustment valve one additional turn and retry the choke procedure.

Note that choke only works while engine is turning. There is no accelerator pump so pumping gas pedal has no effect.

Idling and very short repeated trips will foul plugs. Engine needs half hour running at 40 mph or so to warm engine and clean carbon off the plugs.


If temperature is below 60 or so with cold engine, you may need to choke and or use GAV to start.

Some engines may need a little choke (1 second or so) EVEN with warm engine.

As engine warms reduce amount of GAV used down to 1/4 turn (OR the setting that works best for your engine).

When using choke you may notice that in most cases the engine starts AFTER you release the choke so keep it to about 1 second and remember that the use of GAV might be needed to keep engine running until it warms up!
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Last edited by Benson; 07-28-2018 at 07:37 AM. Reason: spelling and corrections and additions
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Last edited by Benson; 08-01-2018 at 03:51 PM. Reason: ADDED additional info
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Old 07-31-2018, 01:47 PM   #7
Dennis D 1929
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Default Re: Choke rod question

Thanks to all !! Seems to run better at 1/2 turn open, so I'll leave it there for now. Thanks again for all your help.
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Old 07-31-2018, 06:16 PM   #8
31 Deluxe Coupe
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Default Re: Choke rod question

Dennis, thanks for asking the question it was very informative to another newbie.
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Old 08-01-2018, 03:03 AM   #9
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Default Re: Choke rod question

Great question, just as importantly the replies were great.


Gerry, Birch Bay WA
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Old 08-01-2018, 07:06 AM   #10
chap52
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Default Re: Choke rod question

Dennis,
Here is a link to an Instruction Manual in pdf format. It will help in your understanding about these sweet ol' rides. Chap

http://motormayhem.net/wp-uploads/20...ion-Manual.pdf
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Old 08-01-2018, 07:51 AM   #11
BILL WILLIAMSON
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Default Re: Choke rod question

AND, if your GAV affects your idle, YOU'RE IDLING TOO FAST!!!
YES, I repeat a LOT, "REPETITION IS THE MOTHER OF LEARNING & THE FATHER OF BOREDOM"
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Old 08-01-2018, 02:09 PM   #12
Purdy Swoft
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Default Re: Choke rod question

The GAV can and sometimes will effect idle if the carb isn't running on the slow idle circuit . The owner can decide what is too fast idle . Many things can effect how slow an engine will idle . People that want better power and performance are usually not concerned with super slow idle .
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Old 08-02-2018, 03:44 PM   #13
BILL WILLIAMSON
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Default Re: Choke rod question

[B]Some Folks can doodle with the GAV fer a MONTH & still not know what it does?????
I've described it in DETAIL, several times. Go on search and tipe in "GAV" and you'll find my stuff.
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