49 Champion – expansion plug?

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  • July 14, 2015 at 12:17 am #2009
    vintagedave
    Participant

      I have a 1949 Champion 4K. We started it for the first this past weekend, it started and ran well but there is water coming out of a port in the head directly below the spark plug. Looking at a copy of the parts manual I believe it is a missing expansion plug.
      McMaster-Carr has some small metal expansion plugs, also rubber expandable plugs. Can I use either of those? I assume pressure should be pretty low in the cooling line and temperature not too excessive.
      I have a picture of the motor running that shows where the water is coming out, but I’m not sure how to post it.

      July 14, 2015 at 4:16 pm #20132
      garry-in-michigan
      Participant

        Lifetime Member

        An aluminum Expansion plug is best – rubber is the worst.

        July 19, 2015 at 11:32 pm #20425
        vintagedave
        Participant

          I ordered stainless, dish style expansion plugs from McMaster today, hopefully that’s all that I need.
          Here’s a link to a video of the motor running.
          https://www.youtube.com/watch?v=nhlI8L0baFo

          July 19, 2015 at 11:56 pm #20428
          legendre
          Participant

            FYI – when searching for disc-shaped plugs of this type, the following terminology may be of use.

            Plugs that are convex (domed) on the outer face are generally termed ‘Welch plugs’, and they are slightly undersized. They are always driven up against an internal shoulder, and seal by expanding radially as the dome is pushed inward.

            Those plugs that are concave (dished) on the outer face, often with deep rims, are termed ‘core plugs’ or ‘frost plugs’, and they are slightly oversized. They may or may not be driven against an internal shoulder, and seal as the rim compresses in the slightly undersized plug hole.

            July 20, 2015 at 1:20 am #20432
            vintagedave
            Participant

              There is a slight shouler inside the opening. The plugs that I ordered are .377", I measured the opening at .380".
              I’ve installed cup style automotive freeze plugs before, but this is my first attempt at this size and style. I’ll take all of the advice I can get.

              July 20, 2015 at 3:29 am #20438
              hotrod
              Participant

                It may overheat if you run it with visible water coming out. The only place water should come out is the tube outlet just above the prop, which is underwater. Like Frank said, it is a closed siphon system. Water goes up one line from the pump, through the powerhead, and down out the other line with the aid of syphon action. The expansion plug may be on the way up, preventing water from reaching the cylinders water jackets if it leaks.

                July 21, 2015 at 1:44 am #20510
                legendre
                Participant
                  quote VintageDave:

                  There is a slight shouler inside the opening. The plugs that I ordered are .377″, I measured the opening at .380″.
                  I’ve installed cup style automotive freeze plugs before, but this is my first attempt at this size and style. I’ll take all of the advice I can get.

                  Sounds like a welch plug to me, and it’s in the typical size range. I’ve never seen a welch larger than about 3/4", though they may certainly well exist.

                  Easy enough to install. Make sure the bore is clean, and there is no dirt or corrosion pushed up against the shoulder. Secure the workpiece well, set the plug in place, and secure it by dimpling the dome with a round, flat punch of the appropriate diameter. I believe the rule is to use a punch that’s 2/3 the diameter of the plug. Drive the dome in just enough to secure the plug fully, do not drive it so far that it goes below flush, and collapses inward or you risk losing the fit.

                  If you do goof up, drill a hole in the center of the plug, thread in a sheet metal screw, and use that screw to pull the ruined plug out. Try again with a new plug.

                  July 21, 2015 at 2:10 am #20513
                  vintagedave
                  Participant

                    Very helpful, thank you. Parts should be here by Wednesday, hoping to give it a try on Saturday. I’ll post an update.

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