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leaking carbs

Discussion in '1965-1970 Shelby Mustang GT350 & GT500' started by chris67gt500, Apr 9, 2006.

  1. Apr 9, 2006 #1
    chris67gt500

    chris67gt500 Member

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    First off, I spent alot of money (locally) rebuilding my BJ and Bk carbs. they look great, but consistently leak a huge amount of gas from the throttle linkage areas onto my manifold. They don't leak from the bowls.

    Holley says this is caused by boiling gas at high temps which causes the overflow, and can be cured with the use of a phenolic heat spacer between the carb and the manifold.

    Any thoughts? Anyone have the same problem?
     
    chris67gt500, Apr 9, 2006
    chris67gt500, Apr 9, 2006
    #1
  2. Apr 10, 2006 #2
    roddster

    roddster Well-Known Member

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    There are seals in the base plate for the throttle plate shafts. Did those get replaced during the rebuild(s)?
     
    roddster, Apr 10, 2006
    roddster, Apr 10, 2006
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  3. May 25, 2006 #3
    BillH

    BillH Well-Known Member

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    Two things to consider here:
    1) This could be caused by heat boiling the gas in the carbs. I had a 427 Fairlane with a single 4V carb (3255). With the LeMans bowls the car was miserable to drive in the summer. Swapped out later design center-pivot bowls and cured the problem.
    2) Did you use genuine Holley parts for your exact application in your carb rebuild? There is a difference in the needle and seats. Some have a large diameter needle tip that contacts the float, some have a contact that is quite a bit smaller, they look the same but are not interchangeable. The design of these parts affects how fuel is controlled. If the float level it too high, you will have a problem with fuel spilling out of the booster venturis and running down the throttle shafts. By design, Holley throttle shafts are not sealed. Fuel running out here is an indication of high float levels.
    Good Luck
    Bill
     
    BillH, May 25, 2006
    BillH, May 25, 2006
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  4. May 25, 2006 #4
    chris67gt500

    chris67gt500 Member

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    Here is my update:

    I checked my floats and found them to be well within recommended levels.
    I replaced by needles/seats.
    I bought a pair of phenolic spacers (3/8") and installed them.
    The carbs are elevated more, of course, but it seem the air cleaner doesn't rub on the inside of the hood.

    The problem is 100% fixed.

    I notice some difference in the power curve during acceleration, and this might be due to the higher carb placement over the intake, but I'm not well versed in the physics of such things, so I can't be sure. But otherwise I consider the fix a success.

    thanks for the tips everybody.
     
    Last edited by a moderator: May 26, 2006
    chris67gt500, May 25, 2006
    chris67gt500, May 25, 2006
    #4
  5. May 25, 2006 #5
    daltondavid

    daltondavid Well-Known Member

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    nice to see a fix be successful!! I plopped a new set of Holleys on mine and hope to dyno tune them this weekend.
     
    daltondavid, May 25, 2006
    daltondavid, May 25, 2006
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