1968 Quadrajet throttle bushings and leakdown

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500, 472, 425, 368 Discussion, 1968 Quadrajet throttle bushings and leakdown in Cadillac Engine Discussion; I've built several q-jets and I know the typical problems with worn throttle bores and well plug leakdown, but I'm ...
  1. #1
    man1ey's Avatar
    man1ey is offline Cadillac Owners Member
    Automobile(s): 1968 Deville Convertible
    Join Date
    Aug 2005

    1968 Quadrajet throttle bushings and leakdown

    I've built several q-jets and I know the typical problems with worn throttle bores and well plug leakdown, but I'm about to do it again and I would like your ideas.

    On the throttle bushing solution, do you recommend doing it myself using one of the kits online that come with a drill bit and brass bushings? I don't have a drill press and I don't know if I'm going to get the angle close enough.

    Also regarding the bushings, I'm not even sure I have to do it. To test, I sprayed ether right on the outside of the bore while the car idled. On the driver's side, there was no effect. On the passenger side, there was a significant drop in idle. That indicates the bore is elongated on the passenger side. Agree?

    And last of all on the well plugs - I've fixed them with cheap epoxy and marine epoxy and nothing holds long enough. If you've ever tapped the well plugs and fit them with a threaded plug, I'd like to hear how that went for you.

    Age-old questions I know! But I've researched all the solutions and I'm not convinced on a couple of things. I want to hear from people who have tried 'em.


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  3. #2
    deVille33 is offline Cadillac Owners Connoisseur
    Automobile(s): 1977 Coupe (blue), 1977 Coupe (yellow), 1977 Coupe (green)
    Join Date
    Mar 2006
    Western Massachusetts

    Re: 1968 Quadrajet throttle bushings and leakdown

    Doug Roe's illustrations recommend using a drill press to repair the bores. I have seen the wells capped with brass plugs. I didn't investigate further. They appeared to be pressed in. If they used a sealer, I don't know.

  4. #3
    BRUCE ROE is offline Cadillac Owners Fanatic
    Automobile(s): Eldorado
    Join Date
    Jun 2009

    Re: 1968 Quadrajet throttle bushings and leakdown

    I had a V8 that would idle nicely at 500 rpm. Trouble was, the idle speed kept changing. I finally found, the the butterflies didn't always close to the exact same position. The throttle bearings were worn, and sometimes things would move around and bind. A bigger problem than air leaking past bushings. Bruce Roe

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