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06-16-2021, 09:39 PM | #1 |
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Join Date: Apr 2012
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Fuel/air mixture setting
Just changed plugs. I had been running way too rich and the old plugs were really fouled. Test drove the car a few miles and ran so much better with new/clean plugs. I turned the mixture control all the way (clockwise) lean to get the starting point to set the mixture about 1 1/2 to 1 3/4 turns rich based on suggested guidelines. When I got all the way toward lean I expected the engine to falter a bit but with it all the way clockwise I couldn't tell any difference in the way it ran. Do I need other adjustments or is that OK? This is a 1930 Model A roadster and the carburetor is a Zenith.
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06-16-2021, 09:57 PM | #2 |
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Location: michigan
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Re: Fuel/air mixture setting
I think you might have a dirty carb there is a vent hole that sometimes gets clogged the hole goes from the cap jet and the gas get a gasket set and take it apart soak it good and blow out every orfice
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06-17-2021, 12:22 AM | #3 |
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Re: Fuel/air mixture setting
in the owners instruction book it says that good drivers can get excellent gas mileage driving with gav all the way closed
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06-17-2021, 12:30 AM | #4 |
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Re: Fuel/air mixture setting
The valve was all the way closed for the first 10,000 miles in my car till I put a down draft on it. Not all engines are created equal.
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06-17-2021, 05:39 AM | #5 |
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Location: Largo Florida
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Re: Fuel/air mixture setting
If you have a Zenith they the GAV should not need to be that far open. It should run fine at about 1/4-3/4 turns open. If not then there is something wrong with it that should be able to be fixed fairly easily. These are simple carburetors and a lot of us have quite a bit of knowledge about them.
Also, what spark plugs are you using ? |
06-17-2021, 07:07 AM | #6 | |
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Re: Fuel/air mixture setting
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Quote:
the car. The GAV is set about 1/8 of turn open to start and warm up, can drive at that setting or completely closed.
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06-17-2021, 07:47 AM | #7 |
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Re: Fuel/air mixture setting
(1) Last step in a tuneup is carburetor adjustment, so ignition refresh including timing comes first;
(2) Engine at operating temperature & GAV 1/4 turn open; (3) Starting at 1.5 turns open, turn idle air screw in or out to get the highest idle speed; (4) Adjust idle speed screw.
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06-17-2021, 03:06 PM | #8 |
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Re: Fuel/air mixture setting
Thanks for all the good answers. Sure do appreciate your comments. First thing I'll do is re-set the mixture control to almost closed---runs great like that. Thanks again.
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06-17-2021, 05:08 PM | #9 |
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Re: Fuel/air mixture setting
No. In God you trust.
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06-17-2021, 05:16 PM | #10 |
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Join Date: Apr 2012
Posts: 141
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Re: Fuel/air mixture setting
Overlooked answering the questions about what plugs I used: The ones I removed were Champion C-4. Checked replacing those with the same thing, however when I checked the price with one of the Model A suppliers they are $37.00 each. Went to a local NAPA dealer and bought Champion 561 plugs (that is the number on the box. Four of those were $33.00 total. Anyway, the new plugs run great. I'll keep the old C-4 and clean them up.
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06-17-2021, 05:29 PM | #11 |
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Re: Fuel/air mixture setting
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06-17-2021, 05:57 PM | #12 |
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Re: Fuel/air mixture setting
My Coupe runs perfectly okay with the GAV closed. This probably indicates a damaged GAV needle seat. Probably not the needle as I had replaced it. My plugs are cleanest with the GAV closed, so I run that way.
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06-17-2021, 07:26 PM | #13 |
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Re: Fuel/air mixture setting
Open up the GAV one full turn if you are running 100% alcohol.
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06-17-2021, 08:14 PM | #14 | |
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Re: Fuel/air mixture setting
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06-17-2021, 08:24 PM | #15 | |
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Re: Fuel/air mixture setting
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