carburetor Ills

[Woodie1]

I have a 2 dr that we have had on the road for 44 years. I am at the point that the carb is giving me fits. The mileage dropped from around 14 to about 9. I have also noticed that the idle air mixture has to be 2 1/2 turns out to get the best speed out of it at idle. It used to run best about 1 1/2 turns out. It was stopping some times when I came to a stop. I set the float higher so there is less gas in the bowl. I wouldn't have thought this would affect the gas mileage. It hasn't been dying at stops anymore though. Any ideas?

[100IH]

GAV simply adds more fuel above idle speed to what is coming through the main jet. Sounds like your not getting any from the main jet. #2 float level does significantly affect richness. #3 Possibly confused language here. -- when you set the float level, the top of the carb. is upside down. If the float is raised, the fuel level will be lowered and will lean out the mixture to the engine. I would think that in 44 years "we" would be more on top of things by now. Best of luck. By the way, there are hundreds of threads on carburetor issues that can be found in the advanced search function. Dive in with GUSTO, learning this stuff is great fun.

[Marshall V. Daut]

I assume you have a Zenith carb, which the Model A came with from the factory? No matter what carb is on your car, though, it's dirty inside and needs to be disassembled and completely cleaned, especially the idle areas. Either drill out the plugs and clean the passageways or try using the paper clip tool to check passageways. Using compressed air, blow out all orifices and each jet. Your breath is not strong enough to dislodge junk inside the passageways. High pressure is your friend here.
If it's a Tillotson, it still needs to be disassembled and cleaned, but additionally the mounting flange will most likely need to be leveled out with a good file. It warps in the middle and sucks air inside through this "saddle" low spot, which throws off the air-to-fuel mixture. Of all the Tillotsons I have reluctantly gone through for friends and customers over the years, I almost always end up drilling out the lower passageway because it is easily clogged. It's easy to reach and drill out, followed by a smaller drill bit turned by hand to clean out the junk. I usually end up drilingl it out at slow speed. That really turns the carb's performance back on.
Marshall

[jhowes]

I wish I knew the answers to your delima. 14 mpg is way to low for an A.You apparently run a Zenith as the others don't seem to stall when you come to a fast stop. I found that the best mileage and economy is with a Marvel. Been running one for years now and I average over 20mpg. Others will tell you to get a new carburetor or have yours rebuilt and they are probably right. Each to his own. Jack

[Corley]

Sorry, but I'm confused by what you said. You said you raised the float so there is less gas in the bowl. That would be backwards, unless you meant that you raised the float level while the carb was upside down. Please clarify...

Probably best to just set the float to spec. in any case. (Did you shake it to make sure it is not partially full of gas?)

[Woodie1]

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The float level was checked with the top half of the carb upside down. I know that the theory always was the seam of the float should be parallel to the machined surface & the fuel level should be 5/8" below the machined surface of the bottom half of the carb. I have a book by Gordon Bigger who did a book on restoring the Model A carburetor the "Rex Reheis" way. In the book on page 21 he talks about float level & states that Rex felt it was better to have less gas in the bowl. He set another shim under the float needle to raise the float to 1 5/16" when the upper casting is held inverted, looking at the front end where the gas goes in. This is what I followed this time since I could not resolve the problems. I have usually used welding tip cleaners to clean the jets but....I only use the largest cleaner that will go into the jet without using the rasp portion of the tip cleaner. I refrain from enlarging the jets.

[100IH]

Pencil filter in the tank? Have you removed the fuel line from the carb. and loosened the line at the top to blow through the line and the valve to dislodge rust? Have you removed the main jet and and the jets in the bottom of the bore for the airflow to check for blockage? If you go to Berts, they have a great trouble- shooting site for the carburetor.

[Ed in Maine]

The recommendation to get the book Model A Carburetor the "Rex Reheis Way" is excellent. As part of this book is the procedure to flow test your jets. I had poor carbs for years and it wasn't till I flow tested jets that all the problems went away! Good luck, Ed

[WHN]

If I correctly understand what you said. 44 years is a great run for any carburetor.

Time to take it apart and rebuild.

It’s nice owning something (Model A) for that long. Enjoy.