49 Champion – expansion plug?

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  • vintagedave


    Replies: 6
    Topics: 3
    #2009

    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.


    garry-in-michigan

    Lifetime Member
    Replies: 3583
    Topics: 31
    #20132

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


    vintagedave


    Replies: 6
    Topics: 3
    #20425

    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


    legendre


    Replies: 389
    Topics: 8
    #20428

    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.


    vintagedave


    Replies: 6
    Topics: 3
    #20432

    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.


    hotrod


    Replies: 119
    Topics: 7
    #20438

    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.


    legendre


    Replies: 389
    Topics: 8
    #20510
    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.


    vintagedave


    Replies: 6
    Topics: 3
    #20513

    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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