Problem Found When GAV turned Out Too Much

[marc hildebrant]

Group,

In another post, I had talked about having the GAV turned out almost 0ne turn to run O.K. I had looked into the needle\holder of the GAV as a possible problem. Since then, I have found the real problem (I think).

The total problem was :

If I set the idle with the GAV open around 1\4 turn, the car would idle poorly and stall when I applied the brakes at an intersection. The car would run well at speed.

I replaced the carburetor with an old Tillototson that I had. Idle now was good with no stalling with the GAV 1/4 open.

I believe that the idle circuit needs to be cleaned. The carburetor was a rebuilt Zenith that I bought about three years ago.

Marc

[RawhideKid]

Marc, the float level on the Zenith is way too high, filling the bowl with too much fuel. When you take it apart, turn the top upside down and adjust the washers under the float valve to set the float seam parallel with the top. On the ones I have done it is about 1.050 to the seam edge.

[Brian T]

When idle speed is set correctly --- around 500 rpm there should be no response from the GAV at idle, you may be correct about cleaning the jets and setting the float level, be sure you set the idle speed as mentioned, in an earlier post you stated you had the GAV 2 turns out, I would think that would be to much even on your frosty days in winter with a warm engine.

[BILL WILLIAMSON]

Chief taught me, "To set the GAV, with engine warm, run at a steady 20 to 25 MPH in second, then adjust the GAV for BEST/SMOOTHEST running"---"After that, if it STARTS/RUNS OK, don't ever DOODLE with it"!!!---"It might need further adjusting, when the weather's BITIN' COLD"!! (BRRRR!)
AND, like someone else said, "IF the GAV affects the idle, you're idling TOO FAST"
The GAV is OFTEN mis-understood---Go to modelabasics.com & see how it functions.
Chiefs' Student

[marc hildebrant]

Bill,

Thanks for the info on the web site. Good stuff.

Your comment "Chief taught me, To set the GAV, with engine warm, run at a steady 20 to 25 MPH in second, then adjust the GAV for BEST/SMOOTHEST running"---"After that, if it STARTS/RUNS OK, don't ever DOODLE with it"!!!---"It might need further adjusting, when the weather's BITIN' COLD"!! (BRRRR!)" Is somewhat puzzling as the GAV seems to work with the "CAP" jet
and is only for low speeds ? 20-25 in second would be high speed for the motor ?

Marc

[1931 flamingo]

Sponsored Links (Register now to hide all advertisements)

20-25 in 2nd NOT going to hurt anything while you play with the GAV. JMO
Paul in CT

[marc hildebrant]

Paul,

Agreed....

My question was more along the idea that the GAV isn't doing much at those speeds.
Now, to be honest I do not totally understand the Zenith Carburetor's operation and maybe the GAV should be adjusted at speed ?

Marc

[BILL WILLIAMSON]

Marc,
The GAV is a wholly separate jet, that can be turned off, or used to supplement the MAIN JET, when extra fuel is needed, partly dependent on Altitude/Temperature/Humidity/ETC.
If your idle speed is around 500 RPM, the GAV WON'T affect your idle. On Minerva, I ran all the time with it closed, except for a cold, late night run to the store & it was 1/2 warmed up. It would be "flat" on acceleration, until I opened it 1/2 turn. Many Zeniths vary on their needs for GAV use. Sorta' like people, that have different ways of digesting information !
HOPE this HELPS.
IF you get tired of seeing my NAME & hearing me RATTLE ON, just tell ME! & I'll go sit in a FETAL position, in the corner. (With the DOG!)
Bill Practical

[Big hammer]

Originally Posted by BILL WILLIAMSON

Marc,
The GAV is a wholly separate jet, that can be turned off, or used to supplement the MAIN JET, when extra fuel is needed, partly dependent on Altitude/Temperature/Humidity/ETC.
If your idle speed is around 500 RPM, the GAV WON'T affect your idle. On Minerva, I ran all the time with it closed, except for a cold, late night run to the store & it was 1/2 warmed up. It would be "flat" on acceleration, until I opened it 1/2 turn. Many Zeniths vary on their needs for GAV use. Sorta' like people, that have different ways of digesting information !
HOPE this HELPS.
IF you get tired of seeing my NAME & hearing me RATTLE ON, just tell ME! & I'll go sit in a FETAL position, in the corner. (With the DOG!)
Bill Practical

Your input is much needed, no sitting in the corner We need you to keep hammering the information in to our thick head! Set it and forget it.... sounds like Tom W's timing set it and leave it along!
Bill thank you for your information!

[Brian T]

Originally Posted by BILL WILLIAMSON

Marc,
The GAV is a wholly separate jet, that can be turned off, or used to supplement the MAIN JET, when extra fuel is needed, partly dependent on Altitude/Temperature/Humidity/ETC.
If your idle speed is around 500 RPM, the GAV WON'T affect your idle. On Minerva, I ran all the time with it closed, except for a cold, late night run to the store & it was 1/2 warmed up. It would be "flat" on acceleration, until I opened it 1/2 turn. Many Zeniths vary on their needs for GAV use. Sorta' like people, that have different ways of digesting information !
HOPE this HELPS.
IF you get tired of seeing my NAME & hearing me RATTLE ON, just tell ME! & I'll go sit in a FETAL position, in the corner. (With the DOG!)
Bill Practical

Excellent post Bill.

[BILL WILLIAMSON]

I try HARD to give practical, simple advice. I only offer advice that has worked for me, personally!
If I'm not sure, I put it in "quotation" marks,----Like, "maybe" or "might"---The Dog does the same thing & he knows a LOT of stuff, he always reads with me & listens a LOT!
Bill W. & Buster T.

[marc hildebrant]

Gang,

Well, after a couple of nice road trips around the Cape, the operation of the GAV now works the way it should.

Starting cold, open about one turn. Warmed up, 1/4 turn. No backfires from the carb and doesn't stall after a hard stop.

The Zenith that needed the GAV always one turn out most likely has "crud" inside the idle area that is bypassed by the GAV.

After I open up the bad boy Zenith, I will give it a good cleaning and then put it back. Then, I'll rebuild the Tillotson that I'm currently using as a spare.

Marc