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Thread: Engine Carb Newbie

  1. #1

    Default Engine Carb Newbie

    Hi all, and thanks for letting me in. I'm a newbie at engines and carbs and I have some questions regarding my Edelbrock/Holley engine in my boat.

    The engine is a GM 5.7L V8, it was new and installed in 2015/2016. I bought the boat midsummer 2018, but after a few weeks I started experiencing some problems on low speed/Idle. It ran super rich and I believe it was only running on 7 cylinders. I tried several things to fix it. I adjusted the carb (without any skills), got new spark plugs and at last added some fuel treatment to get rid of potential water in the fuel. The fuel treatment seemed to work and the engine was running normal again.

    Since then I'm experiencing the same problem each time I refuel. I have to add fuel treatment in order to avoid the problem.

    I have some questions though, regarding the behavior and symptoms. I know I should give you guys more info on the engine/carb. Is there a model number somewhere on the carb that I can look for? (All I have at the moment is the attached picture of the engine.)

    - In general, the engine seems to run rich on low RPM. I'll try to adjust that with vacuum gauge later today, but should the screws be adjusted clockwise or counterclockwise to achieve a leaner mixture?

    - Sometimes, when I experience the problems described above, the engine stops completely when shifting gear (low RPM). When that happens, I can see that it is leaking gas from the carb and on to the engine. Might there be another problem causing this or can it be a normal consequence of rich mixture -> not running on all cylinders -> stalls?

    Best regards, Morten Westby
    Click image for larger version. 

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  2. #2
    Join Date
    Jan 2010
    Location
    Brisbane, Australia
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    1,941

    Default

    The list number is stamped on the front of the choke air horn.
    Lean is clockwise.
    Have you checked the float levels?
    Where does this fuel leak appear to come from? Gary
    Regards, Gary

  3. #3

    Default

    Looks like it's coming from below the choke. I haven't checked the float levels, I don’t know how to.

  4. #4
    Join Date
    Jan 2010
    Location
    Brisbane, Australia
    Posts
    1,941

    Default

    List number please?
    Here is a video for float level adjustment:
    https://www.youtube.com/watch?v=LKEonVeOXco. You could have a bad needle valve, sunken float.

    Looking at your photo, I would say you have a very basic 600 vacuum secondary with non-adjustable needle & seats. The dry float level has be set correctly with the fuel bowls off. More than likely you need a carb rebuild. Gary
    Last edited by Gaz64; 06-02-2020 at 06:26 PM.
    Regards, Gary

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