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Spark Knock

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  • Spark Knock

    Does spark knock happen only at higher RPMs or once it starts, it lasts through lower RPMs also?
    1988 26' cuddy
    1975 20' open
    16' Sandpiper
    14' Certified Fiberglass

  • #2
    Knock or preignition happens through the entire rpm range but is directly related to timing. So if your distributor isn't operating properly it can occur at certain points and go away at others.
    Atlantic City, NJ
    1982 Cuddy, Rebuilt 351 .060 rings, Edelbrock carb

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    • #3
      PS. It can damage cylinder heads, walls, rings and valves not to mention bearings. Needs attention sooner that later.
      Atlantic City, NJ
      1982 Cuddy, Rebuilt 351 .060 rings, Edelbrock carb

      Comment


      • #4
        Changing octanes in gas can cause it after the engine is tuned. Water in gas can too.
        Atlantic City, NJ
        1982 Cuddy, Rebuilt 351 .060 rings, Edelbrock carb

        Comment


        • #5
          Jerry, just thinking about your new engine and it's increased performance, you may need to run high test(octane) gas because of higher compression and heat characteristics. Octane is a rating of how the additives in gas increase resistance to preignition(knock).
          Atlantic City, NJ
          1982 Cuddy, Rebuilt 351 .060 rings, Edelbrock carb

          Comment


          • #6
            Anything wrong with running at 6* timing?
            1988 26' cuddy
            1975 20' open
            16' Sandpiper
            14' Certified Fiberglass

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            • #7
              I got taught that you retard timing for more power and advance it to increase efficiency. With a vacuum advance system, as the vacuum decreased the timing was retarded and as the vacuum increased the timing was adjusted mechanically. With the centrifical advance you start at a fixed point and as the weights spin faster the timing decreased to add power to each firing. 6* might fix the problem but I'd try the high test first. Jmho
              Last edited by Ship; 08-12-2022, 06:38 PM.
              Atlantic City, NJ
              1982 Cuddy, Rebuilt 351 .060 rings, Edelbrock carb

              Comment


              • #8
                Octane boosters, do they work? Which one is best? How much do they boost the octane? 89 octane is $1 cheaper than 93 octane.
                1988 26' cuddy
                1975 20' open
                16' Sandpiper
                14' Certified Fiberglass

                Comment

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