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Thread: Crankshaft question

  1. #21

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    Hey Brian, I have a bearing service manual and troubleshooting guide. In that manual it shows bearings that are like what you describe. It can be caused from lugging the motor. You mentioned you towed heavy loads with it. Do you recall lugging it much? I guess it can happen with or without a towed load. Anyway, I thought I would post that. Lugging can cause you to scrub bearings into the under lying babbit material...A.T.

  2. #22

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    The reason lugging is tought on bearing is that when the engine is lugged it isn't turning up the RPM, in turn not building good oil pressure, and the cylinder pressure and load squeeze the oil layer to the point where I cannot support the load and the bearing comes in contact with the crank. Don't be afraid to keep it one gear lower when pulling a good load. I had a friend with a bulldozer trailer and dump truck that replace the bearing three times in the 8 or 10 years I've know him. He runs through the gears as fast as he can and is always lugging it.

    Brian's damage was probably from the oil thinning out...same basic effect...thins to the point it can't support the layer.
    Big Blocks RULE!

  3. #23

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    I got all new bearings today- rod and mains. And some STP and brake cleaner. $71 for Clevite's.

    I have no idea what it was from, since there were so many problems with that motor....or more with me making it. The motor was my first effort and I learned alot, but it cost me alot. There was a while where I had the rockers too tight and it ran poorly and then on only about 6 cylinders. Then I ran it for the majority of it's life with the timing on 16-18*. It also had a messed up oil boss that sent oil shooting everywhere.

    I learned alot, and have repaired alot of the problems that I think lead to this.

    Thanks!!!

  4. #24
    Join Date
    Dec 2003
    Location
    West-central Ohio
    Posts
    689

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    You use the "77" tri-metal bearings? The Michigan77 and the Clevite 77s are the same, different boxes. The factory that makes these is right in my home town. I drive by it on the way to wal-mart all the time. I drink beer with one of the guys in on the inventing of those things. My H.S. shop teacher invented one of the broaching machines in the manufacturing process of them. Got one uncle and one aunt that still work there. Dana bought the factory and rights to the bearings.

    Yup, I'm nearly famous.

    Now for the tech part to keep me from getting bounced - you use STP fro assembly lube? How about some "lubriplate" white grease, instead? and DON"T touch the bearing surface with bare hands! Also, if you ever get a cracked head or other way of contaminating your crankcase with ethylene glycol coolant - flush it with clean engine oil with Rislone addative - it has an ingredient that leeches the coolant out of the mearing material. Coolant will displace the oil in the bearing and not let it build a proper oil cushion - early bearing failure may soon follow.
    "other peoples junk, is something or other" - Militarypotts 02/07/2011

  5. #25

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    Moderator Notice: this topic has been split. The cracked heads thread is it's own topic now. Please refer to the Open Discussion board to continue. Thanks, Evil Nazi Moderator Tacoma
    **I heart Bump_r **

  6. #26

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    B

    It shuldn't be a problem, But if youre concerned put one of the old bearings in the center main and snug it up. that should take care of it

  7. #27

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    I think it has been said before, make sure the back side of the bearing and the bearing cap are spotless. No oil, rag fibers, dirt ect... That will change/reduce your clearances. Have fun and good luck...
    Liz, covid, murdered 10/19/21

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