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Autolite 4100 Question

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  • Autolite 4100 Question

    So I decided to bite the bullet and try and rebuild my Autolite 4100 myself. I have next to zero mechanical knowledge but I have enough documentation and Youtube videos on how to do it. Worse case scenario is I just buy a rebuilt one if I screw something up. My question is though, the Primary Throttle Shaft and Lever Assembly plus the Accelerating Pump Rod are both really, really rusty and nasty. Will soaking these in Carb Cleaner remove the rust or should I try and find new ones? I've yet to find just those pieces for sale though.

    Any help?

  • #2
    If its really that bad you will be fighting an uphill battle. Post a picture and someone can make a recommendation. Perhaps you can ask Santa for a new carb??


    • #3
      The throttle shafts are brass so a soaking in carb cleaner and a light buffing should clean those up. The smaller metal parts can be cleaned using a wire brush or a light sanding if they are rusty.

      John Pizzi - Squarebirds Administrator

      Thunderbird Registry #36223 856-779-9695


      • #4
        Carb cleaner is a solvent and will remove the grease, grime and crud. Use that first then separate out the steel parts that are rusted for additional treatment.

        If at all possible, leave the throttle shafts intact by NOT unscrewing the two screws at each throttle plate. The plates are carefully positioned at the factory then after the screws tightened, the ends are pressed in to prevent them from backing out. Nothing worse than having your engine swallow a screw, then have the plate hang up at high engine speed. Use a wire brush on a dremel to clean these steel plates up, followed by detergent and hot water, then rinse and dry with a clean paper towel. Finally, use a light spray of carb cleaner to absorb and remove all the remaining moisture.

        Rust on small steel parts like linkages and screws can be removed easily using Muriatic acid. NOT for brass and aluminum. Follow all precautions. I like to use disposable glad ware, disposable nitrile gloves and do it outside with the wind behind me. Do not soak for more than 30 seconds or so, agitate, then remove from the bath and immediately soak in detergent and water, then rinse and dry.


        • #5
          Ed's Carburetor Forum

          You might try over there if you need a part or 2. I got one that way. I went through my 4100 a couple of times before I learned how susceptible these carbs are to vacuum leaks which can lead to lean running and inability to adjust idle mixture. The trick is to make sure EVERY flat surface that is sealed with a gasket is as flat as possible. Secondary diaphragm cover, power valve cover plate, accelerator pump cover, the body of the carburetor...all flat surfaces. Time/repeated assembly/over-torquing screws can lead to warped surfaces. Some folks use a flat file to repair the surfaces. Whenever possible, I used a piece of 100 grit sandpaper on a flat surface to take out the warpage. I polished my throttle shafts with a brass brush and followed with very fine sandpaper. Care must be exercised on the shafts. They are another common place for vacuum leaks.

          Good luck.



          • #6
            Originally posted by bbogue View Post
            YCare must be exercised on the shafts. They are another common place for vacuum leaks.
            Very true. Back in the day my old daily driver had an Autolite 2100. I had so many miles on the car that the brass throttle shaft had ovaled out the linkage side of throttle body. A starving student with no money, I enlarged the outside of the bore slightly to accept an O ring. Then I threaded the end of the shaft to accept a washer and lock nut, and used that to compress and seal the O ring. I drove the car for several years and many more miles after that.