Compression Loss

Discussion in 'Flat Fender Tech' started by stang7222, Aug 21, 2017.

  1. Aug 21, 2017
    stang7222

    stang7222 New Member

    Long Beach...
    Joined:
    Jul 9, 2011
    Messages:
    23
    '51 L-head losing compression in cylinder 3 through the spark plug. I know this from spraying soapy water around the plugs. •Problem get worse as engine heats up. •New plugs didn't fix a thing.

    Any suggestions on fixing this?
     
  2. Aug 21, 2017
    Howard Eisenhauer

    Howard Eisenhauer Super Moderator Staff Member Sponsor

    Tantallon, Nova...
    Joined:
    Nov 22, 2003
    Messages:
    4,535
    What do the threads look like?

    What kind of condition is the seat in?

    Might be cheaper/easier just to get another head, walcks has reconditioned ones for $270.

    H.
     
  3. Aug 21, 2017
    stang7222

    stang7222 New Member

    Long Beach...
    Joined:
    Jul 9, 2011
    Messages:
    23
    The threads look ok. The plug seems thread in normally. The seat isn't in bad shape. It's definitely showing it's age though.
     
  4. Aug 21, 2017
    rusty

    rusty Well-Known Member

    norfolk,va
    Joined:
    Dec 16, 2006
    Messages:
    1,530
    You could try making a small thin gasket for the plug. Look for any cracks in the seat. If any you may try j b weld or some sort of metal sealant that can take heat and pressure. New head may be in your future.
     
  5. Aug 22, 2017
    PeteL

    PeteL Member Sponsor

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    Aug 3, 2003
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    5,230
    Does the plug have it's gasket?
     
    cookieman likes this.
  6. Aug 23, 2017
    garage gnome

    garage gnome Rust polisher Sponsor

    Western MA
    Joined:
    Jun 19, 2009
    Messages:
    1,467
    Put the head in a bridgeport and use the correct size end mill to clean up the spark plug seat. I've done that before and it works great.
     
  7. Sep 2, 2017
    teletech

    teletech Member

    Live Oak, CA
    Joined:
    Aug 20, 2016
    Messages:
    67
    Sounds like the seat has enough pitting that you can't get a seal.
    Defiantly the right way to go, clean them all up while you are there and then put something in there to prevent the rust.
    Of course, if you don't want to pull the head... You could try a small copper gasket in addition to the factory plug gasket. I also recently had some surprisingly good results from something I bought at O'Reily, right next to the muffler putty (which might just work as well), it was some sort of "high heat weld", spread a little on the plug and screw it in, cure at 100F for some hours (sounds like under the hood in the sun should work) . For something like $10 and a few minutes of your time it might be worth a shot, worst case is it makes the plug hard to remove from the head you were already going to have to take off.
     

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