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Champion j7 spark plugs

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  • Champion j7 spark plugs

    I have't had a Stude since 1989, so what plugs are best suited for my 1950 champ? I've been told j8's will work fine. OK?

  • #2
    I've done more research than I care to admit on spark plugs, initially spurred by the desire to find out what the correct spark plug was for a '56 Golden Hawk. There's a spreadsheet on my web site that has some interchanges for spark plugs listed on it. a J-8 might be OK as long as you don't drive it too hard, that will be a hotter plug than a J-7. An Autolite 306 or AC 44 is listed as a direct interchange.

    Whatever you do, though, don't buy a champion plug with a "Y" in the part number as that will be a "projected nose" type plug which works great in an OHV engine but will get all kinds of smashed up by the piston in a side valve engine - there isn't enough clearance in there for the longer nose. I believe AC denotes a projected nose by an "S" suffix and the Autolite numbering system is too cryptic to explain in detail here, but IIRC they do have an explanation in .pdf form on their web site.

    If you do use my web site as a cross reference, I have the most confidence in the Autolite and AC numbers, just so you know. I think that some of the Bosch numbers are pretty good but I don't have a lot of faith in the NGK numbers - they list the same plug as crossing to a whole mess of other mfgr's numbers.

    oh yeah, the address is

    62 Daytona hartop
    64 Daytona convertible (in boxes)
    55 Commander Starlight