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Thread: Wyllys MB engine rebuilt hard to turn

  1. #1
    Junior Member
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    Wyllys MB engine rebuilt hard to turn

    Hi guys,
    I am curently restoring a motor pool 1944 MB tub with a GPW frame.
    I Sent the entire engine to a machinist an when I got it back I notices many mistakes where made. So to make a long storry short, I got refund but for the parts and decided I will put it back together myself.
    I do this to have fun and lurn so now is the time I guess.

    All went fine but I think I made a mistake and it is here that I need all your wisdom. Before inserting the rope seal, I had it sit in motor oil for at least one and a halft week. When I took them to install, The black coating was all gone and it had swollen prety much. I had two sets but guess what, I had the realy bad idea to put them all at once. I admit that was not verry smart. But what I did then was to shape the seals anyway and install them like that. The cranks got then tight. I figured that was like it should be since all is new and tight.
    I rebuilt the rest without anny issue. I put the engine back in the jeep yesterday to find out that it is so hard to spin that the starter motor barely turns it. I used the hand crank and almost exhousted myself trying to make it spin. It turns but my sons where not strong enoug. Since they are 16 and 21, it is wrong.

    I used plastic gauges for the main bearings and the rods one and it was within the tolerances specs. I will have no choices other than redo it all over again I guess.

    Will be all in for anny advices have all a good day.

    Stéphane

  2. #2
    Super Moderator bmorgil's Avatar
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    Stephane, I would not soak the rope seal. It will swell and become difficult to install correctly. Your engine is turning over to hard no question. I would loosen the rear cap and if the crank turns easier it is quite possible the seal is applying too much pressure.

    With a rope seal the crankshaft (no rods or pistons hooked up) should turn freely with about 10 to 15 ft lbs of rotating torque once it breaks loose and starts moving. With a rubber seal it should spin fairly free, you should be able to spin it by hand. As you add pistons and rings, each assembly should add about 5 ft lbs of rotating torque. So you could end up with around 35 to 40 ft. lbs. of rotating torque on an assembled lower end with no spark plugs installed. If it goes much over that you should take a look. A bearing may be in wrong or there may be interference somewhere.

    If you have to repair the rear main seal, I would use the metal backed rubber seal instead of the rope. You can install the metal backed rubber seal without pulling the crankshaft back out. The rubber works much better in many ways.

  3. #3
    Junior Member
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    Hi thanks for your advices.
    I have a seal from Best seal # 3B71-1. is that good?
    Thanks
    Stéphane

  4. #4
    Junior Member
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    Is best seal # 3B71-1 any good?
    I have one in hand so I am wondering

  5. #5
    Super Moderator bmorgil's Avatar
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    I am not familiar with that brand, but I am sure it is OK if it is for your motor. It should be a metal backed seal.

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