Carburetor Vacuum Question - NCRS Discussion Boards

Carburetor Vacuum Question

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  • Joe L.
    Beyond Control Poster
    • February 1, 1988
    • 43203

    Carburetor Vacuum Question

    Yes, every-now-and-then even I have a question to pose. I need some information on the idle vacuum situation at a certain port(s) for any/all of the following carbs:

    1966 L-72----Holley #R3247A

    1970 LT-1----Holley #R4555A

    1971 LT-1----Holley #R4801A

    1971 LS-6----Holley #R4802A

    What I'm interested in is whether or not the vacuum fitting on the PASSENGER side of the carburetor exhibits PORTED vacuum or FULL MANIFOLD vacuum. It is VERY EASY to check this. With the engine running, simply remove the rubber line from the fitting and check to see if significant vacuum is present with the engine at idle. If little or no vacuum is present, then that fitting has PORTED vacuum; if significant vacuum is present, then that means it's non-ported, full manifold vacuum.

    If there is more than 1 port on the PASSENGER side of the carb, please chack both. If there is more than 1, then there will be one on the throttle body and one on the air horn, both towards the forward end of the carb.

    Thanks
    In Appreciation of John Hinckley
  • John L.
    Very Frequent User
    • December 1, 1997
    • 409

    #2
    Re: Carburetor Vacuum Question

    Joe -- The 66 L72 Carb 3247 is definitely ported vacuum

    Comment

    • John L.
      Very Frequent User
      • December 1, 1997
      • 409

      #3
      Re: Carburetor Vacuum Question

      Joe -- The 66 L72 Carb 3247 is definitely ported vacuum

      Comment

      • John L.
        Very Frequent User
        • December 1, 1997
        • 409

        #4
        Re: Carburetor Vacuum Question

        However the choke break off is manifold vacuum

        Comment

        • John L.
          Very Frequent User
          • December 1, 1997
          • 409

          #5
          Re: Carburetor Vacuum Question

          However the choke break off is manifold vacuum

          Comment

          • Joe L.
            Beyond Control Poster
            • February 1, 1988
            • 43203

            #6
            Re: Carburetor Vacuum Question

            John-----

            Thanks for the info. If the 66 carb side vacuum fitting is ported vacuum, then I fully expect the later ones are, too. The 66 carb is the one that I thought most likely to have full manifold vacuum at this fitting.

            I'm glad to hear that the choke pull-off is full manifold vacuum; that may be helpful.
            In Appreciation of John Hinckley

            Comment

            • Joe L.
              Beyond Control Poster
              • February 1, 1988
              • 43203

              #7
              Re: Carburetor Vacuum Question

              John-----

              Thanks for the info. If the 66 carb side vacuum fitting is ported vacuum, then I fully expect the later ones are, too. The 66 carb is the one that I thought most likely to have full manifold vacuum at this fitting.

              I'm glad to hear that the choke pull-off is full manifold vacuum; that may be helpful.
              In Appreciation of John Hinckley

              Comment

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