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Whimpy F Head

Discussion in 'Early CJ5 and CJ6 Tech' started by 3b a runnin, Jun 26, 2017.

  1. Jun 26, 2017
    3b a runnin

    3b a runnin Active Member 2023 Sponsor 2022 Sponsor

    virginia
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    For a while I thought it was just me and the bigger motors. It seemed like the f head was way behind on power from where it was when I first built it. Really I just figured it was the stronger engines in the other Jeeps. The more I drive the others, the more I thought there was something amiss in the f head.
    During the past winter, I checked the compression in the little 134. A solid 100 psi. in all cyl. Not good, but not critically low either.
    I checked the compression today and was even more disappointed, 90 psi. in all cyl. So I dribbled a little oil in all the spark plug holes and tried again. Got 125-130 in all cyl. Big difference.
    I only have 3-4k on it since the rebuild, (pitiful lifespan). I made the mistake of using an Omix engine kit, so I am suspecting the rings are very poor quality. Block was bored .030 over, so it was trued up during the build.
    Anyone have problems like this, or thoughts as what my problem might be? Any help appreciated!
    Tim
     
  2. Jun 26, 2017
    PeteL

    PeteL If it wasn't for physics, and law enforcement... 2024 Sponsor 2023 Sponsor 2022 Sponsor

    Hills of NH
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    Sticky or stuck rings? Try some MMO?

    I don't know why but it seems every older F-head I've ever owned had busted rings, even with only 20 or 30 thousand original miles. Maybe because they sit all winter? IDK.
     
  3. Jun 26, 2017
    3b a runnin

    3b a runnin Active Member 2023 Sponsor 2022 Sponsor

    virginia
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    thanks Pete
    I'll try that, the odd part is, it don't smoke any at all like it should with worn rings.:n:
     
  4. Jun 27, 2017
    Keys5a

    Keys5a Sponsor

    Florida Keys
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    Were valves and cam/lifters changed out with Omix parts? Or just rings, bearings, etc? Poor quality valves can cause some of your low power as they pit and erode at the seat area.
    -Donny
     
  5. Jun 27, 2017
    Glenn

    Glenn Kinda grumpy old man Staff Member

    Apopka, Fl
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    Have you retorqued the head? Lately? Or after you first rebuilt it?
     
  6. Jun 27, 2017
    1960willyscj5

    1960willyscj5 Well-Known Member

    Mesa, Arizona
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    What's your timing set at?
    Using fresh gas or what is in the tank?
    Why do you let it sit all winter? CJ's are excellent snow vehicles.
    Might want to run some Sea Foam through the fuel system.
    Where did you get your rebuild kit?
    I just looked at Rock Auto. The rebuild kits for the Willys F-134 engines are all Omix-Ada. Does noone else even offer one anymore?
     
  7. Jun 27, 2017
    3b a runnin

    3b a runnin Active Member 2023 Sponsor 2022 Sponsor

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    I actually blew a head gasket last summer, so yes that was replaced.

    IIRC the timing is at 5 btdc,
    As for gas, yes its fresh, I have ran several tanks through it this summer. All were non ethanol.
    Again IIRC that would have come from KW.
    The camshaft and lifters were not changed. The valves were changed, and hardened seats were installed. The block and heads were decked, new pistons, rings, bearings, & oil pump.
    I haven't tried seafoam.
     
  8. Jun 27, 2017
    PeteL

    PeteL If it wasn't for physics, and law enforcement... 2024 Sponsor 2023 Sponsor 2022 Sponsor

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    Re-adjust the intake valve-lash at that time?
     
  9. Jun 27, 2017
    3b a runnin

    3b a runnin Active Member 2023 Sponsor 2022 Sponsor

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    yes, I did adjust the valves. I'm really thinking worn rings here but it don't smoke any. Cranks easy, don't sputter, seems perfect, except has no power. It does seem hard to get above 3000 rpm while driving it. I guess it just don't have the power to overcome the wind resistance. There are some fairly steep hills around here, and some are impossible to top out at 30 mph. Recently installed an OD in this Jeep, and 2nd OD does help some, but just not enough. I'm about to the point of parking it until I figure out what is wrong.:cry:
     
  10. Jun 27, 2017
    Glenn

    Glenn Kinda grumpy old man Staff Member

    Apopka, Fl
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    But did you retorque it after that? After you drove it a bit and it was good and warmed up?
     
  11. Jun 27, 2017
    3b a runnin

    3b a runnin Active Member 2023 Sponsor 2022 Sponsor

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    yes, I did retorque after the head gasket job, actually twice. (I do enjoy tinkering with my Jeeps)
     
    Glenn likes this.
  12. Jun 27, 2017
    Glenn

    Glenn Kinda grumpy old man Staff Member

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    Did you check the compression after the initial rebuild? Maybe a few hundred miles on it?
     
  13. Jun 28, 2017
    Twin2

    Twin2 not him 2024 Sponsor 2023 Sponsor 2022 Sponsor

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    there you said it . Hills . in high range it just won't go up hill . and make any kind of speed . but in low range the 4 cylinder would shine . no speed required
     
  14. Jun 28, 2017
    Glenn

    Glenn Kinda grumpy old man Staff Member

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    If it has points check the gap. How do the spark plugs look?
     
  15. Jun 28, 2017
    Howard Eisenhauer

    Howard Eisenhauer Administrator Staff Member

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    Get or build a leak down tester, that will tell you what the problem is, whether it be rings, sticky valves, leaky head gasket/whatever.

    You should definitely be able to go up even steep hills at better than 30 MPH, 40-45 would be a more reasonable speed.

    Double check your timing.

    H.
     
  16. Jun 28, 2017
    ITLKSEZ

    ITLKSEZ Hope for the best, prepare for the worst

    Liberty Lake, WA
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    Maybe the new rings were garbage. The compression rings will fail before the oil rings, since the oil rings will be better lubricated. That might explain the low compression with no smoke.

    See if you can find some NOS rings and just replace them with a quick hone.
     
  17. Jun 28, 2017
    Daryl

    Daryl Sponsor

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    It all depends on the hills. No F head is going up our hills here over 30 no matter what. There simply isn't enough horsepower and the 9" brakes will not stop you going down the other side either. Hard to understand if you live somewhere that is flat.You did state that it doesn't have as much power as it used to. That would lead me to believe that something has gone wrong. I would start back at square one and assume nothing while checking everything having to do with fuel delivery, spark, timing and even have a oil sample tested to see if anything has broken down internally.
     
  18. Jun 28, 2017
    Keys5a

    Keys5a Sponsor

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    Pull your distributor cap and see if the rotor easily twists a couple degrees and springs back. The spark advance can stick from lack of lube and can definitely affect the power.
    -Donny
     
  19. Jun 28, 2017
    Glenn

    Glenn Kinda grumpy old man Staff Member

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    I was thinking along this line also, including the thought that maybe the rings never really seated good to begin with. It would be nice to know what the compression was to begin with.
     
  20. Jun 28, 2017
    PeteL

    PeteL If it wasn't for physics, and law enforcement... 2024 Sponsor 2023 Sponsor 2022 Sponsor

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    Low compression may be a shaggy dog. Maybe your gauge is bogus, for instance.
    Sometimes "poor performance" can be a stuck brake or a too-strong throttle spring, etcetera.

    In any case a tune-up to spec is always the first place to start - especially points, and timing including checking the advance.
     
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