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F 134 Valve Train Issues

Discussion in 'Early CJ5 and CJ6 Tech' started by Oldpappy, Aug 19, 2022.

  1. Aug 19, 2022
    Oldpappy

    Oldpappy A.C. Fults - Curmudgeon at large 2022 Sponsor

    East Tennessee
    Joined:
    Feb 8, 2021
    Messages:
    1,620
    The F 134 in my 67 was running strong. It smoked a little on crank up, but cleared after warming so I figured the seals were going south.

    A while back it suddenly started running rough, and smoking badly. I also noticed black oily looking stuff in the air horn of the carburetor, and when I pulled the plugs #3 was fouled. New plugs and it ran better, but still a little rough, and when I put my hand over the carb I could feel a fluttering blow back and got black stuff on my hand which I determined wasn't oil but probably partially burnt fuel.

    The flutter at the carb had me thinking all sorts of bad thoughts, but after a dialog with "Oldtime" I went at the diagnosis with a few new ideas.

    I found the issue, and since it involves something I had not encountered before thought it might help someone else if they have similar troubles.

    Here is how I proceeded and what I found.

    First thing I did was compression tests. Cylinders 1,2, and 4 showed good compression, cylinder 3 was low, and didn't change at all for the wet test.

    Valve timing was not the problem, but Ken (Oldtime) described a good way to check this without pulling the timing cover. That saved me a lot of work. I would have hated to have pulled the front off the engine and not found the problem.

    The smoking was from some pretty worn valve guides, and I think it suddenly got worse because the old seals finally failed the rest of the way.

    The thing that had me puzzled was feeling some fluttering blow back out of the carb when I put my hand over the air horn, and getting that black crud on my hand, I was able to feel it and smell it. I decided it was not oil but burnt fuel or carbon.

    When I pulled the head I found the number 3 intake valve wasn't sealing, and all of the guides showed wear.

    So, I took the head into Dover's Cylinder Service, which is an old school machine shop I have used many times. They noticed the retainer for that leaking valve had cracked. This is what I have never seen happen before.

    I just picked the head up from the machine shop today. It has a set of NOS valves I got from Ken last year, NOS guides, and of course new seals. They welded that retainer and did a good job of it, but I want to find a replacement before I install the head.
     
    Last edited: Aug 20, 2022
    Rick Whitson, Fireball and Glenn like this.
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