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Thread: Gas on throttle shaft and puddling

  1. #1
    russeleo Guest

    Default Gas on throttle shaft and puddling

    After I shut my car off and come back out the next morning there is gas on the throttle shaft and puddled on the intake. What causes this?

    ANSWER:
    This is usually caused by percolation. This is when the engine is shut off and the engine temperature rises it causes the fuel to boil in the bowl and leak out of the boosters. There are a couple of things you can do to cure this one is make sure the fuel level is not too high. You can also lower the fuel level about 1/8" below the sight plug hole and this will cure it sometimes. The heat from the engine will rise into the carburetor sometimes and will cause the fuel to boil. Installing a phenolic heat spacer between the carburetor and the intake or a heat shield can cure this. These parts will prevent heat from getting to the carburetor and boiling the fuel.

  2. #2
    JimW Guest

    Unhappy

    How hot does the carb have to get for percolation to occur? I have the same problem that I've been battling? My manifold is at 160 degrees when I come off the road. I have a low budget phenolic spacer. I've lowered the float level as recommended - problem still occuring.

    I have inline GM with an Offy intake that is heated by an attached heat plate that supplies coolant to the base of the intake manifold. I've thought about disabling the coolant plate on the manifold and trying for several days and see what happens, but I'm sure I will have poor driveability due to the cold manifold.


    Any suggestions are appreciated (I'm beginning to get annoyed with the smell of gas whenever I get in) and thanks.

  3. #3

    Default

    Quote Originally Posted by JimW View Post
    "......... I have a low budget phenolic spacer. I've lowered the float level as recommended - problem still occuring........"
    how think is the phenolic block. 1/2" should be the minimum. And if your carb is getting so hot that the fuel is boiling, then you don't need a manifold heat plate.

    Z.

    '66 GT-350 Original Drivetrain, Sheet-Metal, Interior, & Paint

  4. #4
    Join Date
    Mar 2010
    Location
    Bowling Green KY
    Posts
    15

    Default

    Quote Originally Posted by JimW View Post
    How hot does the carb have to get for percolation to occur? I have the same problem that I've been battling? My manifold is at 160 degrees when I come off the road. I have a low budget phenolic spacer. I've lowered the float level as recommended - problem still occuring.

    I have inline GM with an Offy intake that is heated by an attached heat plate that supplies coolant to the base of the intake manifold. I've thought about disabling the coolant plate on the manifold and trying for several days and see what happens, but I'm sure I will have poor driveability due to the cold manifold.


    Any suggestions are appreciated (I'm beginning to get annoyed with the smell of gas whenever I get in) and thanks.
    Jim,
    If the fuel in your area contains Ethanoyl depending on the blend the fuel can begin to boil as low as 100*F-400*f.
    Thanks, Travis
    Holley Performance Products
    Technical Service Representative

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