4180C Help needed!

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  • Junkyardave
    Junior Member
    • Oct 2018
    • 4

    4180C Help needed!

    Hello. I acquired an '86 F250, 460 with a 4180C. There's fuel dumping out of the booster venturis at idle. Here's what I've done so far:
    Lowered both floats (no fuel running out level plugs), new power valve, closed butterflies almost completely, adjusted both idle mixture screws, blocked off EGR valve. Any thoughts?
  • 81 TransAm
    Senior Member
    • Nov 2014
    • 2238

    #2
    Check the air bleeds on the top of the carb to make sure they are not plugged.

    Comment

    • Junkyardave
      Junior Member
      • Oct 2018
      • 4

      #3
      Will do, thank you!

      Comment

      • Junkyardave
        Junior Member
        • Oct 2018
        • 4

        #4
        I may have figured out what's going on. Apparently, the throttle plates are supposed to be completely closed, and the idle screws are supposed to set the idle speed as well as the mixture. Once the throttle plates begin to open, the "transfer slots" make the vacuum drop in the power valve chamber, which starts dumping fuel out the boosters. Those stupid idle screws are a pain to get to, but I think that with some adjusting, it just might work. Any thoughts anyone?

        Comment

        • 81 TransAm
          Senior Member
          • Nov 2014
          • 2238

          #5
          No, you're not correct. Get someone that knows a little about Holley carbs to set it up for you.

          Comment

          • Junkyardave
            Junior Member
            • Oct 2018
            • 4

            #6
            Thanks, 81, but I'll have to figure it out myself. I realize the plates have to be open a certain amount in order for enough air to enter. I could make it idle by hand-choking it, but even with the plates barely cracked, I could still see fuel dripping from the boosters. So maybe there's a vacuum leak. It'll be a week or so before I can mess with it again, so we'll see what happens. Thanks for your help! ��

            Comment

            • 81 TransAm
              Senior Member
              • Nov 2014
              • 2238

              #7
              If there's fuel dripping out the boosters at idle, the fuel level in the bowls is too high or there are air bleeds plugged.

              Comment

              • Gaz64
                Senior Member
                • Jan 2010
                • 2243

                #8
                The siphon break bleeds in the metering block main well could be blocked.
                How many barrels are doing this at idle?
                Primary blades should be open about 1/2 after kissing the lever.
                Mixture screws about 1 1/2 out form seated.
                Adjust from there. Gary
                Regards, Gary

                Comment

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