Fuel leak at inlet fitting - how to seal properly?

Discussion in 'The Venerable Q-Jet' started by weinh, Oct 14, 2019.

  1. weinh

    weinh Well-Known Member

    Today I noticed smell of gas as I worked on optimizing the distributor timing curve. Was not hard to find the cause, the big fitting at the Q-Jet inlet, where the paper filter sits in, slowly dripped fuel. The gas line fitting was dry.
    After disassembly of the large fitting I wondered how this thing is supposed to seal. The threads are interrupted by a number of notches/grooves (blue arrows), making it difficult to seal with teflon tape and the like. And then there is also a red colored paper seal (green arrow), is this doing the sealing task?

    So how do I properly seal this? Do's and dont's, every hint is welcome.
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  2. 436'd Skylark

    436'd Skylark Sweet Fancy Moses!!!!!

    It should seal with a crush washer. No need for teflon tape there or the flare fitting.
    Donuts & Peelouts likes this.
  3. telriv

    telriv Well-Known Member

    That fitting is one of the repair fittings for stripped out threads. The reason for the notches is they cut new threads in a previously bad casting or stripped out threads. The ONLY WAY TO FIX THIS PROPERLY IS TO SEND THE CARB. OUT & GET A Heli-Coil installed along with a new fitting of the proper size.

    Tom T.
    techg8 and Donuts & Peelouts like this.
  4. TORQUED455

    TORQUED455 Well-Known Member

    Like Tom said, that carb inlet nut is a self-tapping “quick-fix”. They shouldn’t even sell them. Judging by the looks of the carb, it needs to have a proper Helicoil repair along with a rebuild.
  5. LARRY70GS

    LARRY70GS a.k.a. "THE WIZARD"

  6. telriv

    telriv Well-Known Member

    Problem is Larry that CANNOT be used in the early carbs.
  7. LARRY70GS

    LARRY70GS a.k.a. "THE WIZARD"

    I know Tommy, just sayin.:)
  8. weinh

    weinh Well-Known Member

    Many thanks to all, thats valuable info for me.
    Before going into a rebuild, I'll try one of those nylon seals first, maybe that solves the issue.
    The threads in the casting do not look too bad and performance wise I cannot complain a bit, the carb apparently does an excellent job, even if the outside appearance is not the best. ;)
  9. telriv

    telriv Well-Known Member

    Doubtful, but it's worth a try
  10. John Osborne

    John Osborne Well-Known Member

    The reason the fuel filter is twisted is the fuel nut is too short. Get the heli-coil installed and get a longer factory type nut.
    When you install the filter, spring, and nut, take a pocket screwdriver, insert it into the center hole in the nut (where the fuel will enter), until the end of the driver contacts the rear of the filter. You should be able to push the filter .060” - .125” against spring pressure.
    Thanks, John
  11. LARRY70GS

    LARRY70GS a.k.a. "THE WIZARD"

  12. Cliff R

    Cliff R Well-Known Member

    Installing a heli-coil is the only good repair for this issue. I've done thousands of them at this point. It's better for us if we get the carb BEFORE the owner rips all the good material out of the front of the casting with oversize fittings, JB Weld, and other attempts to seal things up there.

    Get rid of ALL the Teflon tape, it is NOT needed as the filter housing seals on a gasket, and the fuel line seals on an inverted flare.......Cliff

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