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Thread: What im seeing with my 134 in my 48 CJ

  1. #1
    Junior Member
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    Mar 2022
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    What im seeing with my 134 in my 48 CJ

    So I did a compression check prior to starting to pull the motor, she runs cool and not bad but leaks badly and I want to do a rope seal
    I found 120 in three cylinders and 100 in number 4........This cylinder was the one that the prior owner had to change the piston as it was badly seized
    The walls on this cylinder are scared and look bad
    I stuck a feeler gage in each cylinder and found 10 thousands total and 15 in number 2 cylinder, so im figuring 5 thousand and 7 1/2 all around piston to wall clearance
    So its decision time and all opinions are greatly welcomed
    I have to pull the crank obviously, I guess I could just do the seal and put it all back together or I could rebuild and hope the cylinders clean up at 80 over
    Now if I was young and broke I know what id do but at my age while im still turning wrenches and enjoying it, pulling the engine a second time is not appealing
    What id like to know is are those clearances acceptable and what about the compression
    Thanks

  2. #2
    Super Moderator bmorgil's Avatar
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    Dec 2018
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    Northwestern Ohio
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    It does appear like a rebuild might be in order. The compression test procedure on this is important. There isn't a lot of compression there to begin with. It is a low compression engine. The process is to watch the compression as it builds, and only give it 4 total compression strokes. You are looking for how much compression you get with each stroke. On a warm engine, in 4 strokes it needs to be 90 - 110 on a L134. The pressure should come up quickly (80% or so) on the first stroke. and after 4 strokes be within specification and within 10 psi of each other. If it fails this test a little oil can be added to see just where the leakage is. You have visually seen a scored cylinder. The finish on the cylinder and the piston and ring fit are some of the most important things you have on a good running, long lasting engine.

    Unfortunately you can't check piston to wall clearance at the top of the piston with a feeler gauge. The piston is "cam" ground or "barrel" shaped. Because of this it is tightest down around the wrist pin, or bottom of the skirt. The top of the piston is where the most clearance would be and the cylinder does not wear at the very top.

    Since it is running now I am sure it will clean up with minimal boring and a finish hone. I don't know how many compression strokes it took to get your compression readings but, the numbers indicate it is still sealing somewhat. I think if you want to be sure you wont need to eventually pull it anyway, pull it now and visit the machine shop with it.
    Last edited by bmorgil; 10-27-2022 at 08:35 AM.

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