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Technical Flathead dragster help

Discussion in 'Traditional Hot Rods' started by Dakota Kid, May 21, 2018.

  1. Dakota Kid
    Joined: Feb 20, 2007
    Posts: 531

    Dakota Kid
    Member

    Checking the plugs on my flathead. Gap is closed almost completely on 2 cylinders on PS rear and DS front cylinders..... I can see where it is hitting the valve. These are old Evans heads on basically stock cam motor. The heads take the larger thread 129 plug. Do they make a index washer for these? Any other ideas? Thickernhead gasket. These heads came off an old dirt track motor and are probaly planed down? 20180521_224456.jpg 20180521_224436.jpg 20180521_224605.jpg IMG_20180518_203523_408.jpg

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  2. big duece
    Joined: Jul 28, 2008
    Posts: 4,921

    big duece
    Member
    from kansas

    Would not hurt to pull a head and wad up a small ball of tin foil, or clay and mock up the piston to head clearance to see what your quench is. Just throwing on a thicker head gasket without measuring, may create other issues. I would bet there is some washers that would lift the plug out of the hole, if your quench is good.
     
  3. alchemy
    Joined: Sep 27, 2002
    Posts: 12,513

    alchemy
    ALLIANCE MEMBER

    Is that plug tapered seat? I've never seen a flathead with a tapered seat plug. If not, just put an extra washer or two under the offending plugs.

    I had some new plugs in my Canadian heads once that got their gaps closed by the valves. I just switched to a different brand of plugs.
     
  4. Dakota Kid
    Joined: Feb 20, 2007
    Posts: 531

    Dakota Kid
    Member

    Found some copper index washers for old harley. Gonna try those...

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  5. RichFox
    Joined: Dec 3, 2006
    Posts: 9,280

    RichFox
    ALLIANCE MEMBER

    I'm with alchemy. I think you are using the wrong plugs for these heads. Have the plug seats been machined for taper seal plugs? Or just smashed down by using the wrong plugs? Look into some proper plugs made for gasket sealing.
     
  6. alchemy
    Joined: Sep 27, 2002
    Posts: 12,513

    alchemy
    ALLIANCE MEMBER

    I'm using Autolite 216 now.
     
  7. Cliff Ramsdell
    Joined: Dec 27, 2004
    Posts: 627

    Cliff Ramsdell
    Member

    The autolite 216’s along with the Champion H10’s have a 14mm thread. The plugs the OP has are 18mm thread.

    I’m sure that tapered seat is wrong for his application.

    Maybe an auto lite 386 or a champion 502 would be better suited being a gasket seat, 18mm thread plug.

    Cliff Ramsdell
     
  8. Bored&Stroked
    Joined: Jan 14, 2005
    Posts: 4,014

    Bored&Stroked
    ALLIANCE MEMBER

    Those are the wrong plugs and the heads have been modified for 18mm plugs at some point. I believe you'll be okay once you get the correct plug in it - as it is a stock motor.
     
  9. RichFox
    Joined: Dec 3, 2006
    Posts: 9,280

    RichFox
    ALLIANCE MEMBER

    Or get adapters to go back to 14 mm and a good seal.
     
  10. 6inarow
    Joined: Jan 24, 2007
    Posts: 2,090

    6inarow
    Member

    Randy doesnt know??
     
  11. Pete1
    Joined: Aug 23, 2004
    Posts: 1,506

    Pete1
    Member
    from Wa.

    Get some 18 to 14 adapters. You will have a much wider selection of heat ranges besides curing the gap problem.
     

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