Need Holley Adjustment info - NCRS Discussion Boards

Need Holley Adjustment info

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  • Larry E.
    Extremely Frequent Poster
    • December 1, 1989
    • 1677

    Need Holley Adjustment info

    Hello:

    We just bought a nice #4555 carb for the LT-1 engine. Those 2 little screws on
    top of the carb just below the model number have been changed from the factory
    setting. I'm told the factory set these and put some type of putty on them so
    no one would reajust them. Well mine have been moved. Any idea on how to set
    them? Carb is not on the engine. Believe the screws are to set idle mixture.

    Thanks; Larry
    Larry

    LT1 in a 1LE -- One of 134
  • John H.
    Beyond Control Poster
    • December 1, 1997
    • 16513

    #2
    Re: Need Holley Adjustment info

    Larry -

    Connect a vacuum gauge to a full manifold vacuum source and work back and forth between the two idle mixture screws (adjusting the idle SPEED screw as necessary) to achieve the highest steady vacuum reading. If the idle mixure screws have been disturbed, 1-1/2 turns out from lightly seated is a good starting point.

    Comment

    • Larry E.
      Extremely Frequent Poster
      • December 1, 1989
      • 1677

      #3
      Re: Need Holley Adjustment info

      John:

      Just want to make sure we are talking about the two tiny screws that face up
      right by the top of the air horn. These are not the screws that are on the side
      of the carb. I noticed that not all carbs have these screws. This perticular
      carb is a new remake from Holley for the #4555. Thanks for the help.

      Larry
      Larry

      LT1 in a 1LE -- One of 134

      Comment

      • John H.
        Beyond Control Poster
        • December 1, 1997
        • 16513

        #4
        Re: Need Holley Adjustment info

        Larry -

        Got your e-mail - send me a photo if you can; don't know what the "tiny vertical screws" might be, unless they're removable (vs. pressed-in) air bleeds.

        Comment

        • Clem Z.
          Expired
          • January 1, 2006
          • 9427

          #5
          Re: Need Holley Adjustment info

          those are final adjustment for emissions at idle.i am at the PRI show this week and i will ask the guy at the holley booth who i get my info from

          Comment

          • Clem Z.
            Expired
            • January 1, 2006
            • 9427

            #6
            Re: Need Holley Adjustment info

            these were set on a air box and there is no way to duplicate the setting.best bet is to check the same carb/engine combo that did not use these adjustment screws and use the same air bleed/jet combo and block these adjustment passages.

            Comment

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