Carberator Adjustment for a 1930 Model A

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    I have a 1930 Model A, 7 passenger sedan and I have been trying to locate some information on how to adjust the carborator. The car runs well but appears to be running rich. I have not been able to locate any liturature on adjustments so anything would be appreciated.


    hi sid,

    click on the “library”” button to the left they have 15 manuals including the parts and owners manual for the 1930 model A. the owners manual should andswer your question. the library is a great tool and when you call them they respond super quick. i got manuals etc for my series 33 within a week of when i ordered and their price is good. hope all is well with your series 36.

    george quay”


    Hi Syd, the carb on the ’30 cars only has an idle screw for adjustment. The mainjets are fixed jets. Unless the mainjets have been changed, then usually the orginal jets are too lean for today’s fuels mixed with alcohol. If I remember correctly, the jets are stamped on the outside with the jet size, maybe you can read this number with a mirror and post it here, and someone with a similar car/engine can compare their jetsize to your’s.

    The only other ‘adjustment’ would be the float level, if the fuel level is high, it will run a bit richer.

    What indications or symptoms do you have that lead you to think it’s running rich? Heavy black smoke out the exhaust? Fouled spark plugs? Or??

    If your points have closed up [usually from the rubbing block wearing down], this will retard the spark, which can give some symptoms similar to a too-rich mixture. Have you tried to run the spark advance lever near full advance? Have you checked the distributor to see if the automatic centrifugal advance is working correctly? A non-functioning centrifugal advance will make the car sluggish and not burn all the fuel because the spark is too late.

    That’s all that I can think of.

    Greg Long


    Check the idle discharge tubes, they often plug up causing the car to idle on the main jet circuit, which will cause it to have a poor idle and a rich condition down low. Also, you must remove ALL THE BRASS PLUGS AND JETS to get the carb cleaned out. Very often they are very difficult to remove. If all the brass cannot be removed, you cannot clean all of the passages. I have seen “rebuilt” carbs with several brass plugs that have not been removed, and thus they suffer idle circuit problems. Good luck, Ed. PS be carefull with the UU-2 as they can crack and fail due to poor pot metal.


    Also, check to see if your idle air adjustment has been modified. Go to this ebay auction number – 110644101070 – be sure to look at all the photos, and you can see what you should have for a stock set up. Remember also that many Pierce cars have had other UU-2 carbs installed, thus ALL of the jets and venturies as well as the accelerator pump are incorrect.



    Stromberg’s specification for the main jet on a 1930 Model A or B Pierce and a UU-2 was .046″. The size is marked on the head of the hex. Of course, this was for 1930 gas which was much “heavier” than modern gas. If you have .046″ jets, then there’s a good chance that the rest of the orifices and such are the correct ones for Pierce as well. If you contact me offline I can mail you a listing of the various UU-2 and UUR-2 specs for Pierce-Arrow as well as other cars. I credit Greg Loftness for compiling it many years ago.



    Bill, Could you post the info you have? Or email it? The only info I have is in a huge book with hundreds of pages, and I must hunt around to find what I am looking for. If the carb was changed out often the main jets were also, but the rest of the parts are often not. Remember a UU2 and UUR2 carb fit on engines from 240 CID to 560 CID and most of the internals if they are incorrect will cause idle, acceleration, and mixture problems. We often see the smaller carbs installed on a Pierce with all the jets and air bleeds opened up in an effort to try and make them run right. They usually don’t. A word of caution to all … don’t run lean and burn a valve or piston! If you must set the carb up yourself use a 5 gas analyzer to check for correct combustion, or be sure to run the car on the rich side to prevent damage. Remember the stuff we pay 3.50 a gallon for is not gas as it was in the old days! Ed


    Thanks to everyone who has provide input it is most useful. Bill , if you could either email or FAX the information to me that would be great. by email is [email protected] and FAX is the same as the home phone 760 433-0383. Thanks again.


    I’ll email it to anyone who wants it. It’s an Excel spreadsheet. Just contact me at [email protected]


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