Reply To: Spark plug info

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November 7, 2022 at 8:09 pm #268768
Mumbles
Participant

    The book sez, ’39 – ’47 Sportman motors were equipped with Champion H-10J plugs gapped at .025″.  You’ll have to do some searching to find a modern equivalent to that plug.

    I’m thinking H is the thread length and 10 is the heat range.  J style plugs with the shortened ground aren’t made or needed anymore.