Timing fluctuates with vacuum advance connected

General Mopar Tech Discussions

  1. RobsRR

    RobsRR Well-Known Member

    Messages:
    119
    Likes Received:
    17
    Joined:
    Dec 15, 2017
    Location:
    NC
    Local Time:
    4:14 PM
    I have tried between 16 and 18 initial no advanced . I think it is around 25 with advance but would have to verify that.

    Another question. Will the advance curve change going from manifold to ported. I know the idle part would but what about after that? It should stay the same at cruise?
     
  2. moparedtn

    moparedtn Ed on the Ridge FBBO Gold Member

    Messages:
    10,710
    Likes Received:
    17644
    Joined:
    May 14, 2011
    Location:
    On the Ridge, TN
    Local Time:
    4:14 PM
    Boy, does Professor Ehrenberg hit it out of the park in that article....but then, he always does.
    ROB - READ THAT ARTICLE.
    Ehrenberg describes your situation to a "T"!
     
    • Agree Agree x 1
    • RobsRR

      RobsRR Well-Known Member

      Messages:
      119
      Likes Received:
      17
      Joined:
      Dec 15, 2017
      Location:
      NC
      Local Time:
      4:14 PM
       
    • 65-440

      65-440 Well-Known Member

      Messages:
      3,136
      Likes Received:
      2628
      Joined:
      Dec 2, 2009
      Location:
      virginia beach, va
      Local Time:
      6:14 PM
      Yes please verify, 25 at idle is high! The again my 340 likes 22 degrees initial!....18 sounds about close to where it should be.
      So you need to drive with a vacuum gauge on the ported source on the carb and see what it does when driving....adjust your canister to that. I believe I have mine to start coming In at 8-10" vacuum....i could be wrong, it's been a while!!
      use a hand held pump to test the can, mark down how many inches it takes to start the movement and how many inches when it stops moving.
       
    • RobsRR

      RobsRR Well-Known Member

      Messages:
      119
      Likes Received:
      17
      Joined:
      Dec 15, 2017
      Location:
      NC
      Local Time:
      4:14 PM
      Do you have a link to the article. You definitely peaked my interest.
       
    • 65-440

      65-440 Well-Known Member

      Messages:
      3,136
      Likes Received:
      2628
      Joined:
      Dec 2, 2009
      Location:
      virginia beach, va
      Local Time:
      6:14 PM
      As far as cruise goes should be in the 48 degrees area, all depends on your total and how much the can applies..
       
    • moparedtn

      moparedtn Ed on the Ridge FBBO Gold Member

      Messages:
      10,710
      Likes Received:
      17644
      Joined:
      May 14, 2011
      Location:
      On the Ridge, TN
      Local Time:
      4:14 PM
      As @turbine68rt has kindly provided in post #8 of this thread....
       
      • Thanks! Thanks! x 1
      • RobsRR

        RobsRR Well-Known Member

        Messages:
        119
        Likes Received:
        17
        Joined:
        Dec 15, 2017
        Location:
        NC
        Local Time:
        4:14 PM
         
      • RobsRR

        RobsRR Well-Known Member

        Messages:
        119
        Likes Received:
        17
        Joined:
        Dec 15, 2017
        Location:
        NC
        Local Time:
        4:14 PM
        Ok thank you
         
      • Chargered

        Chargered Well-Known Member

        Messages:
        361
        Likes Received:
        467
        Joined:
        Feb 12, 2012
        Location:
        Peosta, IA
        Local Time:
        3:14 PM
      • 1967coronet

        1967coronet FBBO Gold Member FBBO Gold Member

        Messages:
        3,070
        Likes Received:
        3875
        Joined:
        Jun 19, 2014
        Location:
        Iowa
        Local Time:
        3:14 PM
        Right now the focus is on the distributor since he's working on the timing with manifold vac.
        When he runs it with the can unhooked the timing settles down.
        Now let's forget about the distributor and can for a second.
        Put a vacuum gauge on the engine and check it for fluctuation .
        Might be fishing the wrong spot.
         
        • Like Like x 2
        • Bee1971

          Bee1971 Well-Known Member

          Messages:
          1,105
          Likes Received:
          1092
          Joined:
          Jun 22, 2017
          Location:
          Sobieski
          Local Time:
          3:14 PM
          Correct

          Depending on Camshaft duration / lift and Carb idle settings

          Vacuum Fluctuation at idle when distributor is attached to full vacuum

          Camshaft has a lot to do with this

          Bottom line
          Vacuum reading at engine idle - Intake full vacuum

          Vacuum reading that it needs to engage your distributor vacuum canister to start movement

          Then we can go from there
           
          Last edited: Feb 7, 2021
          • Agree Agree x 1
          • moparedtn

            moparedtn Ed on the Ridge FBBO Gold Member

            Messages:
            10,710
            Likes Received:
            17644
            Joined:
            May 14, 2011
            Location:
            On the Ridge, TN
            Local Time:
            4:14 PM
            Am I reading correctly that someone has postulated that erratic timing at idle (vacuum advance
            out of the equation/disconnected) can be the direct result of simply a lumpy cam?
            I got to ponder some on that one...
             
          • RobsRR

            RobsRR Well-Known Member

            Messages:
            119
            Likes Received:
            17
            Joined:
            Dec 15, 2017
            Location:
            NC
            Local Time:
            4:14 PM
            My mighty vac hand pump seems to of disappeared so I will have to buy or borrow one to check the vacuum can.
             
          1. This site uses cookies to help personalise content, tailor your experience and to keep you logged in if you register.
            By continuing to use this site, you are consenting to our use of cookies.