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Misfire 1966 Cruiser

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  • Misfire 1966 Cruiser

    Hey, I don't know if this has been answered on here before, but my car develpoed a misfire on take off afew days ago, which slowly developed to being there all the time, heavy or gental acceleration, and steady speeds, still there. I changed the cap and rotor, and points, which were all very ugly, checked for spark at every wire, its there, could this be a problem in the carb, or something else, I know, theres probably so many different things it could be, but any help would greatly be apreciated

    Eric Harnett
    1966 Cruiser
    Hamilton Ontario
    Hamilton Chapter
    Eric Harnett
    1966 Cruiser
    Hamilton Ontario
    Hamilton Chapter

  • #2
    Without hearing or driving it, it's hard to know for sure. You didn't mention having checked the spark plugs, but this is precisely the way a bad (or fouled) spark plug presents itself. First they start to fail under hard acceleration, when cylinder pressure is highest. As fouling progresses, the miss happens under milder acceleration, and eventually at cruise or idle. Each failed combustion event adds a little to the gunk fouling the plug.

    First thing I'd do (if a road test or inspection didn't reveal some other obvious problem) would be to pull all the plugs and "read" them. Visit your local auto parts store, and look at a spark plug maker's catalog. They will have a photo chart, and an explanation on how to read plugs. The same thing can be found in many car/motorcycle repair books in the book rack. It's basic and universal. You can almost certainly find this on-line, too.

    I wouldn't expect a carb problem to cause a rhythmic and persistent miss, especially a miss confined to one or two cylinders. Carb problems are more commonly manifested by a simple lack of power, or an irregular lope, or most commonly, a "flat spot". That describes the situation where you step on the gas, and nothing happens for a second or so, and then the car slowly accelerates. When it gets really bad, the car will bog or outright quit.

    A regular steady miss can also be caused by a valve or ring problem on the affected cylinder. Reading the plugs may disclose that, too.

    Note: This is exactly the sort of problem that tune-up scopes were designed to solve. "Solve" as in the sense of giving a definitive answer as to the cause of the problem. See if you can find a local tune-up shop that still has a scope, and a mechanic skilled in using it. The obvious place to start your search would be at a speed shop, or performance engine shop. Somebody there ought to be able to direct you to the right mechanic.

    Gord Richmond, within Weasel range of the Alberta Badlands
    Gord Richmond, within Weasel range of the Alberta Badlands

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    • #3
      How about the spark plug wires? How old are they? Watch the engine run at night to see if they are arcing or cross firing.

      Paul Johnson, Wild and Wonderful West Virginia. '64 Daytona Wagonaire, '64 Daytona convertible, '53 Commander Starliner, Museum R-4 engine, '62 Gravely Model L, '72 Gravely Model 430

      Paul Johnson, Wild and Wonderful West Virginia.
      '64 Daytona Wagonaire, '64 Avanti R-1, Museum R-4 engine, '72 Gravely Model 430 with Onan engine

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      • #4
        To me, this sounds exactly like plug wires. You can check for spark and see them working, but under a load the spark can "leak" out through a weak spot in the wire and jump to nearby metal. Start the engine in a very dark area at night and look under the hood- probably you'll see sparks jumping all over. I would bet a new, quality set of plug wires and plugs will fix it!

        Robert (Bob) Andrews Owner- Studebakeracres- on the IoMT (Island of Misfit Toys!)
        Parish, central NY 13131

        "Some people live for the rules, I live for exceptions"- 311

        "Do they all not, by mere virtue of having survived as relics of a bygone era, amass a level of respect perhaps not accorded to them when they were new?"



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        • #5
          OOPS! Me and Paul were responding at the same time

          I can't believe Gord didn't mention wires![:0]

          Robert (Bob) Andrews Owner- Studebakeracres- on the IoMT (Island of Misfit Toys!)
          Parish, central NY 13131

          "Some people live for the rules, I live for exceptions"- 311

          "Do they all not, by mere virtue of having survived as relics of a bygone era, amass a level of respect perhaps not accorded to them when they were new?"



          Comment


          • #6
            quote:Originally posted by bams50

            OOPS! Me and Paul were responding at the same time...
            Hey, just an example of great minds working along the same channels.




            Paul Johnson, Wild and Wonderful West Virginia. '64 Daytona Wagonaire, '64 Daytona convertible, '53 Commander Starliner, Museum R-4 engine, '62 Gravely Model L, '72 Gravely Model 430

            Paul Johnson, Wild and Wonderful West Virginia.
            '64 Daytona Wagonaire, '64 Avanti R-1, Museum R-4 engine, '72 Gravely Model 430 with Onan engine

            Comment


            • #7
              Hey, thanks for all the help, my wires are close to a year old, but they are pretty cheap, I have not started it up in the dark yet, but I will tonight, I did check the spark plugs though, I found the plug from Cylinder #7 fouled with oil,

              I changed the plugs, and its ilding very smooth, havent had a chance to drive it yet

              Eric Harnett
              1966 Cruiser
              Hamilton Ontario
              Hamilton Chapter
              Eric Harnett
              1966 Cruiser
              Hamilton Ontario
              Hamilton Chapter

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              • #8
                Keep in mind, plug wires not firing correctly under load can cause plugs to look like that; and make a new set look that way in a short time, especially if the carb is running a little rich, and/or the car doesn't get many longer trips (common for collector cars). Definitely don't skimp on plug wires!

                Robert (Bob) Andrews Owner- Studebakeracres- on the IoMT (Island of Misfit Toys!)
                Parish, central NY 13131

                "Some people live for the rules, I live for exceptions"- 311

                "Do they all not, by mere virtue of having survived as relics of a bygone era, amass a level of respect perhaps not accorded to them when they were new?"



                Comment

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