VCCA Home Forums TECHNICAL - 1945 AND EARLIER 1937-1945 Fuel Air Mixture Adjustment

Don't get mad, but how do you adjust the fuel/air mixture on my Carter carb(1938 Master Deluxe)? I keep fouling plugs and alot of dark deposits are coming from my exhaust so I read it probably is running too rich. I know this is a basic question, but i have to start somewhere. I initially didn't know where to add motor oil after draining the old.
Thank you for your patience.
Michael
1938 Master Deluxe

No problem Michael. The only questions that won't get answered are the ones not asked. While I don't have the answer to your question regarding adjusting the fuel/air ratio mix there are some things you might want to check first. Check the air cleaner to see if it is causing any air restriction. Also it's good to do a compression test before doing any tune up procedures. Check your manual for air cleaner maintenance procedures. Also check to be sure the plugs are correct for your car. Hang in there and I;m sure one of the carburetor Guru's will advise on adjusting the carb if necessary.

Thank you for the guidance. I also have the vacuum gauge that supposedly can diagnose issues with the different systems(compression, vacuum, ignition). I will read the article and I did pick up from ebay Motors manual that covers my year along with the 1938 Chevrolet Shop Manual. The fun thing about this all is the learning new/old things.
Best Regards
Michael

You might want to make sure the choke opens all the way and check the float level to make sure the bowl doesn't fill too much.

Some possible causes are sinking or incorrectly adjust float. Someone installed incorrect metering rod or rod jet.
Metering rod not syncronized with throtle plate opening ( a gauge made for that purpose), needle and seat bad or incorrect carburetor.

A friend who has a lot of experience as well as his own shop rebuilt the carb for me so beyond any defects i am confident the carb is correct. I will say my breather is a mess in that it is just sitting on top of my carb and it is not correct. I do have the correct breather, but needs to be cleaned up. There probably a collection of small issues that add up to a poorly running engine. I did change the oil and gear box oil a couple of days ago so one step at a time.

Ask him if he had the gauge to syncronize the metering rod with the throttle opening. See the shop manual.

Experience rebuilding carburetors does not mean that it was done correctly. The '38 Carter carburetors are more tricky to get to run correctly. The original jet and metering rod used in '38 carburetors does not produce the best mixture. The later replacement metering rod works much better. A gauge is necessary to properly coordinate the metering rod with the throttle plate. Without that adjustment the carburetor can run either rich or lean.

Do any of you know where a carburetor metering rod gauge for a 37 chev can be bought ?? Thanks,
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Joes 37

A cardboard gauge is contained in some rebuild kits. You can make one that will work. Form a pointed end that fits into the main jet and then 2.795 inches long.

I checked my plugs and they are not fouled, but the car is running a bit rough. I did switch air breathers to the original one. The prior owner(true owner) installed nicer looking filter that was a bit too large and only sat loosely on top of the carb. When I switched breathers the 38 fired right up. I turned the fuel/air screw in until she started to shut off and back out until she smoothened out.
-The breather doesn't seem to require oil and it has a mesh type filter.
-It will get better as I learn what to do.

Thanks Chipper for that idea and the measurement!
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joes 37