The Ford Barn

Houston Rodder · 05-23-2013, 09:50 AM

By turning the choke tube in the cab of my A counter clock wise, am I adding air or gas to the carb? In other words, am I leaning out the carb by opening up the adjustment or richening the mixture with more fuel? In the attached picture I circled the adjustment needle in question.
Thanks

Mitch//pa · 05-23-2013, 09:51 AM

richening

Houston Rodder · 05-23-2013, 09:55 AM

What are the ways you can tell if your vehicle is running too lean or too rich?

Tom Wesenberg · 05-23-2013, 09:59 AM

Keep turning the valve CCW and it should run rougher due to too rich a mixture.

Turn the valve CW and it should slow and run rougher due to too lean a mixture.

Mine runs about the same 1/4 open or closed, so I just leave it closed except during warm up.

Houston Rodder · 05-23-2013, 10:06 AM

When assembling the carb b y the instructions, they say to bottom out the needle and back it off 1 and 1/2 turns. That would be too rich, correct?

Tom Wesenberg · 05-23-2013, 10:21 AM

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Quote:

Originally Posted by Houston Rodder

When assembling the carb b y the instructions, they say to bottom out the needle and back it off 1 and 1/2 turns. That would be too rich, correct?

That's where I turn the knob for cold starts, but I close mine after a minute of running. Most people leave the valve 1/4 turn open.

Mitch//pa · 05-23-2013, 10:21 AM

i run 1/4 open at all times and never really touch it... sometimes at cold start up you can give it more then put it back. all this depends on a properly functioning carb so your results may vary...
to ck mixture,
ck spark plugs for proper burn , a good nose can smell it or a gas analyzer

JD 1931 · 05-23-2013, 10:32 AM

CW = lean CCw = rich. 1 turn out from closed to start, then 1/4 to 1/2 open to run warmed up...

Houston Rodder · 05-23-2013, 10:33 AM

Thanks guys, ya'll are a big help.

Bob C · 05-23-2013, 11:38 AM

Quote:

Originally Posted by Houston Rodder

When assembling the carb b y the instructions, they say to bottom out the needle and back it off 1 and 1/2 turns. That would be too rich, correct?

I think they are talking about the idle mixture screw, #7 in your picture, not the GAV.

Bob

heneste · 05-23-2013, 11:48 AM

If you're running too rich, you'll most likely get black smoke out the tailpipe and possibly increased engine heat. Too lean and you could get backfiring and increased engine heat and lack of power.

Turning the GAV clockwise will screw the adjusting needle into the seat in the carburetor and restrict the Gas flow to the carb (leaning out). Turning it counter-clockwise will open up the passage and allow more gas into the carb (richening the mixture).

Mitch//pa · 05-23-2013, 11:53 AM

Quote:

Originally Posted by Bob C

I think they are talking about the idle mixture screw, #7 in your picture, not the GAV.

Bob

yea i wonder if he started out talking gav and wandered to mixture?????

Purdy Swoft · 05-23-2013, 01:20 PM

Bob C is correct in post number 10 The idle air adjust screw on the upper housing adjustment starts at one and one half turns off the seat. The model B carb runs with the GAV on the choke rod closed, all the way gently to the right after warm up. I usually open the GAV 1/2 turn to the left with a B carb when cold . After it warms a bit the engine will begin to lope and I then turn the gav knob all the way to the right. The model A zenith carbs usually run best with the GAV open 1/4 turn to the left , off the seat.

John Butts in CT · 05-23-2013, 03:53 PM

No needle valve will function as designed unless it closes at full CW rotation, and what's more frustrating than an "adjustment" screw or knob that doesn't adjust anything? So... I have four observations to add:

(1) Make sure that both the GAV needle assembly and the idle mixture screw are the correct length and actually do bottom out in the seat (I've seen versions of both that were so short that they "bottomed out" in the threads long before the needle hit the seat.)

(2) Some repro idle mixture screw springs are too long, and also prevent the needle from seating. Try the screw without the spring, see how much space you have for the compressed spring, and cut the spring to fit. Oh, and make sure that the spring collar (ferrule?) is not too deep, as well.

(3) Make sure that both brass needles are polished, true, and free of scoring.

(4) Make sure that both needle seats are clean and smooth.

Running these checks is a fun, easy, and rewarding workbench job. Get it right and you're good to go for your lifetime.

05-23-2013, 09:51 AM	#2
Mitch//pa BANNED Join Date: May 2010 Location: Bucks County, PA Posts: 11,454	Re: Choke Adjustment Needle? richening

05-23-2013, 09:55 AM	#3
Houston Rodder Member Join Date: Feb 2011 Location: Spring, TX Posts: 55	Re: Choke Adjustment Needle? What are the ways you can tell if your vehicle is running too lean or too rich?

05-23-2013, 09:59 AM	#4
Tom Wesenberg Senior Member Join Date: May 2010 Location: Mpls, MN Posts: 27,582	Re: Choke Adjustment Needle? Keep turning the valve CCW and it should run rougher due to too rich a mixture. Turn the valve CW and it should slow and run rougher due to too lean a mixture. Mine runs about the same 1/4 open or closed, so I just leave it closed except during warm up.

05-23-2013, 10:06 AM	#5
Houston Rodder Member Join Date: Feb 2011 Location: Spring, TX Posts: 55	Re: Choke Adjustment Needle? When assembling the carb b y the instructions, they say to bottom out the needle and back it off 1 and 1/2 turns. That would be too rich, correct?

05-23-2013, 10:32 AM	#8
JD 1931 Senior Member Join Date: Jul 2010 Location: west coast Fla.. Posts: 311	Re: Choke Adjustment Needle? CW = lean CCw = rich. 1 turn out from closed to start, then 1/4 to 1/2 open to run warmed up...

05-23-2013, 10:21 AM	#7
Mitch//pa BANNED Join Date: May 2010 Location: Bucks County, PA Posts: 11,454	Re: Choke Adjustment Needle? i run 1/4 open at all times and never really touch it... sometimes at cold start up you can give it more then put it back. all this depends on a properly functioning carb so your results may vary... to ck mixture, ck spark plugs for proper burn , a good nose can smell it or a gas analyzer

05-23-2013, 10:33 AM	#9
Houston Rodder Member Join Date: Feb 2011 Location: Spring, TX Posts: 55	Re: Choke Adjustment Needle? Thanks guys, ya'll are a big help.

05-23-2013, 11:48 AM	#11
heneste Senior Member Join Date: Nov 2010 Location: Ottawa,Ontario, Canada Posts: 271	Re: Choke Adjustment Needle? If you're running too rich, you'll most likely get black smoke out the tailpipe and possibly increased engine heat. Too lean and you could get backfiring and increased engine heat and lack of power. Turning the GAV clockwise will screw the adjusting needle into the seat in the carburetor and restrict the Gas flow to the carb (leaning out). Turning it counter-clockwise will open up the passage and allow more gas into the carb (richening the mixture).

05-23-2013, 01:20 PM	#13
Purdy Swoft Senior Member Join Date: May 2010 Location: Alabama Posts: 8,099	Re: Choke Adjustment Needle? Bob C is correct in post number 10 The idle air adjust screw on the upper housing adjustment starts at one and one half turns off the seat. The model B carb runs with the GAV on the choke rod closed, all the way gently to the right after warm up. I usually open the GAV 1/2 turn to the left with a B carb when cold . After it warms a bit the engine will begin to lope and I then turn the gav knob all the way to the right. The model A zenith carbs usually run best with the GAV open 1/4 turn to the left , off the seat.

05-23-2013, 03:53 PM	#14
John Butts in CT Senior Member Join Date: May 2010 Location: Southeastern Connecticut Posts: 464	Re: Choke Adjustment Needle? No needle valve will function as designed unless it closes at full CW rotation, and what's more frustrating than an "adjustment" screw or knob that doesn't adjust anything? So... I have four observations to add: (1) Make sure that both the GAV needle assembly and the idle mixture screw are the correct length and actually do bottom out in the seat (I've seen versions of both that were so short that they "bottomed out" in the threads long before the needle hit the seat.) (2) Some repro idle mixture screw springs are too long, and also prevent the needle from seating. Try the screw without the spring, see how much space you have for the compressed spring, and cut the spring to fit. Oh, and make sure that the spring collar (ferrule?) is not too deep, as well. (3) Make sure that both brass needles are polished, true, and free of scoring. (4) Make sure that both needle seats are clean and smooth. Running these checks is a fun, easy, and rewarding workbench job. Get it right and you're good to go for your lifetime.