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Fhead Compression

Discussion in 'Early CJ5 and CJ6 Tech' started by Don X, Apr 24, 2008.

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  1. Apr 24, 2008
    Don X

    Don X The Prodigal Moderator Staff Member 2023 Sponsor

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    Trying to figure out the problem I developed out at Glamis this past weekend. Checked the compression and the 1 & 2 holes showed zero compression. 3 was at 80 and 4 was at 110. I'm no expert but I have a feeling that's not good R)

    My guess is that probably eliminates a valve problem (???) and the head gasket is blown. Am I on the right track or does anyone else have any other ideas?
     
    Don X, Apr 24, 2008
    #1
  2. Apr 24, 2008
    Homebrew2

    Homebrew2 Member

    Dunlap, CA
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    I don't even know you and your story made me sick to my stomach :(

    Any other evidence of blown gasket? ... oil in water, water in oil, bubbles in water. Burned valves, broken springs could be among causes. ... you can see quite a bit of the ex valves with plugs out and mirror.
     
    Homebrew2, Apr 24, 2008
    #2
  3. Apr 24, 2008
    jpflat2a

    jpflat2a what's that noise?

    Hermosa, SD
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    I'm guessing valve problem...
    ex valves or seats
     
    jpflat2a, Apr 24, 2008
    #3
  4. Apr 24, 2008
    Glenn

    Glenn Kinda grumpy old man Staff Member

    Apopka, Fl
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    Blown head gasket in this case is the most likely culprit.
     
    Glenn, Apr 24, 2008
    #4
  5. Apr 24, 2008
    bkd

    bkd Moderator Supreme Staff Member 2022 Sponsor

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    yup.....
     
    bkd, Apr 24, 2008
    #5
  6. Apr 24, 2008
    Don X

    Don X The Prodigal Moderator Staff Member 2023 Sponsor

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    Jim, I know we talked valve out there but is it common for the valves on 2 contiguous cylinders to go out at the same time?
     
    Don X, Apr 24, 2008
    #6
  7. Apr 24, 2008
    jpflat2a

    jpflat2a what's that noise?

    Hermosa, SD
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    possible, but it also had a nice little knock to it off idle
    not real deep either
     
    jpflat2a, Apr 24, 2008
    #7
  8. Apr 24, 2008
    bkd

    bkd Moderator Supreme Staff Member 2022 Sponsor

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    Don if it is a head gasket it's easy enough to pop it off and see...it'll be obvious when pulled
    Jim S.
     
    bkd, Apr 24, 2008
    #8
  9. Apr 24, 2008
    jpflat2a

    jpflat2a what's that noise?

    Hermosa, SD
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    anything is possible
    we don't know what the coimpression readings were before the weekend
    I think a valve seat came apart and the pieces went thru the engine
     
    jpflat2a, Apr 24, 2008
    #9
  10. Apr 24, 2008
    Glenn

    Glenn Kinda grumpy old man Staff Member

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    Ouch! I was hoping for something simple. I didn't know the details.
     
    Glenn, Apr 24, 2008
    #10
  11. Apr 24, 2008
    jpflat2a

    jpflat2a what's that noise?

    Hermosa, SD
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    and you'll see all the valves as well
     
    jpflat2a, Apr 24, 2008
    #11
  12. Apr 24, 2008
    jeeper50

    jeeper50 jeeps 'till I die

    Spanish Fort. AL
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    TAke pics for all us F head fans!
     
    jeeper50, Apr 24, 2008
    #12
  13. Apr 24, 2008
    sdcj6

    sdcj6 Sponsor

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    Counter balanced 2 cylinder Jeep. Rare fuel economy mode. I suggest sand drags on weekends untill total failure. Then swap in spare motor in garage.
     
    sdcj6, Apr 24, 2008
    #13
  14. Apr 24, 2008
    Don X

    Don X The Prodigal Moderator Staff Member 2023 Sponsor

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    R) yeah sure Ray....as long as it's legal R)
     
    Don X, Apr 24, 2008
    #14
  15. Apr 25, 2008
    66CJ52008

    66CJ52008 gone fishin

    Marietta,Ga
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    i got one for yall did a comp test yesterday to see where things are ,all cylinders are reading high according to the book, the readings are 140 to 150 psi , any thoughts on this ?
     
    66CJ52008, Apr 25, 2008
    #15
  16. Apr 25, 2008
    timgr

    timgr We stand on the shoulders of giants. 2022 Sponsor

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    Mmm. I'd suggest you start another thread.

    High is good, consistent is better. Increasing the bore size and surfacing the head will both raise the compression ratio. It's not uncommon to get a mild compression ratio increase on a rebuilt engine. Plus generic compression testers are not precision instruments, and I'm not sure how you would calibrate one.
     
    timgr, Apr 25, 2008
    #16
  17. Apr 25, 2008
    drexotic

    drexotic Happy now?!?!?

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    Bummer !
    Let me know if you need help . . . I've got an engine lift if you decide you need to pull it.
     
    drexotic, Apr 25, 2008
    #17
  18. Apr 25, 2008
    Don X

    Don X The Prodigal Moderator Staff Member 2023 Sponsor

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    Thanks Jeff....I've got a hoist but there's another Fhead sitting on it right now :rofl:

    Tomorrow I try to pop the cylinder head off. If anyone wants to stop by and have a good laugh let me know. R) Any do's, don'ts, suggestions and watch-outs from any of you e-mechanics will be appreciated. I ordered an FSM but it won't be here until next week.
     
    Don X, Apr 25, 2008
    #18
  19. Apr 25, 2008
    Glenn

    Glenn Kinda grumpy old man Staff Member

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    Don't forget the head bolt underneath the carb! :)
     
    Glenn, Apr 25, 2008
    #19
  20. Apr 25, 2008
    Don X

    Don X The Prodigal Moderator Staff Member 2023 Sponsor

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    Thanks for the heads up...I found that one last night when I was poking around.
     
    Don X, Apr 25, 2008
    #20
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