1941 Mercury KB-3 Spark Plug Cover Confusion

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  • Buccaneer

    US Member - 1 Year (includes $3 online payment fee)
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    #271650

    The KB-3 project motor I’m working on was missing the spark plug cover,
    but the stripped down KB-? (missing tag) had one on it.
    The water line and fitting was missing on the motor that had the cover, but
    I don’t see how the cover would have worked on it with the fitting and line
    in place, nor on the KB-3 motor I want to use it on.

    With the 90 deg. fitting screwed into the cylinder, there’s not enough clearance
    for the cover. I thought that perhaps my cover was meant for a “twin” cylinder,
    but when I looked at my KD-4 twin in storage, it has a cover that’s different,
    and perhaps would actually work on the KB-3, having a notch in the area
    where the rubber wedge goes.

    I “may” be able to notch out the cover to make it work, but am wondering
    does anyone have a good photo of a KB-3 with the correct cover in place?

    Thanks.

    DSCN5890

    DSCN5889

    DSCN5893

    DSCN5894

    Prepare to be boarded!


    The Boat House


    Replies: 4521
    Topics: 110
    #271667



    In my files I found this picture of KD-3S
    if that will help ya.
    Tubs


    Buccaneer

    US Member - 1 Year (includes $3 online payment fee)
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    #271673

    Tubs, I see no “tell tale” exiting the back of the cylinder nor
    anywhere else on your photo.
    That’s how my cover looks like currently though……. not
    sure what’s going on!
    I do see that one is also missing the rubber wedge (as Louis calls it)
    between the plug cover and gas tank.
    Thanks.

    Prepare to be boarded!


    Boonie

    Canada Member - 1 Year (includes $3 online payment fee)
    Replies: 203
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    #271682

    I have a friend that makes those spark plug covers ( bra cups). Just finished a KD 4 with ones he made for me.


    green-thumbs

    US Member - 2 Years
    Replies: 583
    Topics: 43
    #271686

    I hang my head in shame, I assumed. I checked the New Parts List and could not find sparkplug covers. Normally that is a good source. Then I looked at assembly charts for KD3 and KD4…KD3 singles use Spark Plug cover M-339  KD4 twins use upper M-337 and Lower M-338, So there are 3 Spark Plug Covers involved. KD3 uses a small fitting with a short section of copper tubing that loops around the spark plug and out thru a notch at bottom. The PreWar singles seem to used the same Upper Spark Plug cover as Twins as the all seem to exit Port side same as twins. The Post War KD3 set up is neater and uses lesst tubing. KE3 changes again to a longer tube that runs doown Starbord side of powerhead. due to sheet metal cowling.

    I still feel Kiekhaefer would use what they had in a limited production KB3, so my money is on use of Upper Cylinder Spark Plug Cover… I can not prove it.

    Louis

     

    T

     


    Buccaneer

    US Member - 1 Year (includes $3 online payment fee)
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    #271694

    Louis, very interesting! So in Tubs photo of a KD-3S the tell – tale may
    indeed be in place, inside of the plug cover, and perhaps barely exiting
    the hole in the bottom of the cup.

    I assumed that the hole in the bottom of the cup was for the spark plug wire?

    I’ll look mine over again tomorrow, but I don’t see any reason why I couldn’t
    notch out the area where the rubber wedge sits, for the 90 fitting to exit
    the cup.
    Not that I have a rubber wedge, but if so, would it still fit in the cup with
    the plumbing in the way? I never did find anyone reproducing them for sale.

    Prepare to be boarded!


    Buccaneer

    US Member - 1 Year (includes $3 online payment fee)
    Replies: 7433
    Topics: 1069
    #271695

    I have a friend that makes those spark plug covers ( bra cups). Just finished a KD 4 with ones he made for me.

    Boonie, if those cups are “repros”, they look excellent!
    Nice looking motor too!

    Prepare to be boarded!


    billw

    US Member - 2 Years
    Replies: 2071
    Topics: 66
    #271696

    Sorry I don’t have the exact picture of how it should be; but these three might help. The FIRST thumbnail picture,the one where there is no cover and no tube, that is the fitting location of a KD3 that is in the proper orientation but missing its copper tubing. There’s supposed to be a very short piece, soldered into the brass fitting, that curves around the spark plug, under the bra cover and exits as shown in my THIRD picture, with the cover on. Second picture is a WB2 that never had a cover. I have no idea what I did, to make the wrong picture the giant one. Sorry.

    KD-2

    Long live American manufacturing!

    • This reply was modified 1 year, 1 month ago by billw. Reason: picture problems
    • This reply was modified 1 year, 1 month ago by billw.
    • This reply was modified 1 year, 1 month ago by billw.

    Buccaneer

    US Member - 1 Year (includes $3 online payment fee)
    Replies: 7433
    Topics: 1069
    #271712

    Thanks for the photos Bill. Heading out to the garage now to take a look and
    “think” about the ordeal.

    Prepare to be boarded!


    green-thumbs

    US Member - 2 Years
    Replies: 583
    Topics: 43
    #271725

    KB-3, KD-3 and KE-3 routed cooling water differently. First year K-1 and K-2 did not have spark plug covers. KE-3 had cowling without spark plug covers.

    Spark plug covers have limited space, compact spark plug MA& be required as well as small ignition wire boot.

     

    • This reply was modified 1 year, 1 month ago by green-thumbs.
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