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450 farmall broken crankshaft


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My son  decided he needed to look at a 450 gas for sale the other day. It had been sitting in the guys shed for the last 20 plus years with a locked up engine. The engine had begun to knock and locked up. He never got around to fixing it and wanted it gone. Really nice straight tractor with not a lot of wear now sitting in my yard !!  We rocked it back and forth and it was locked solid.  Pulled the starter and rocked it some more and the flywheel rocked, but not the front pulley. Dropped the pan and the crankshaft is broke. I don't think I ever heard of a broken crank in one of these old four cylinders before or if it is very common.

I don't know what would break a crankshaft in one of these engines.  Bad crank?   Bad block?  Rebuild this engine or look for another block with a good crank ??

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I got a "parts tractor" that supposed to need a crankshaft. I don't think the block would have to be bad. If things check out the block should be ok. They only have three main bearings and this is possibly a weak point of them

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Take it apart and just see If it spun a main bearing it will need line boring and probably good idea to have the alignment checked anyway

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4 hours ago, bitty said:

 They only have three main bearings and this is possibly a weak point of them

   This is the THIRD FARMALL crankshaft I've heard of,  first was our neighbor's M that a machine shop error planed the head 1/8th inch,  .125" instead of the typical .010" to 100% cleanup. It was still neighbor's fieldwork tractor,  He pulled M-sized implements, IH #8 3-14 plow, 10 ft disk, 4 row planter. He just covered a lot of ground with the tractor.  Yes, the crank broke right behind the center main bearing.  I say it with my own eyes, Dad and I both, in talking with the Father of the M's owner, the owner was plowing right across the creek at the back of the 80 acres my Sister and I own.

    Crankshaft #2 in a Farmall that broke was on a post here at RPM forum about 15+/- years ago.  Can't remember who made the post. The forum has been through a lot of changes since then,  not sure if you can search that far back.

    This 450 crankshaft is broken crank #3 I've ever heard about in a FARMALL engine.  These were all gasoline engines, 3 main bearing engines.

   I'm not really sure this constitutes a "weak spot" in them.  I've read that the early M&W stroker crankshafts suffered quite a few failures when they were used for heavy tillage.  I guess if you REALLY want to lean on an M, maybe figure out how to attach a gasoline head to a diesel block that already has 5 main bearings.  With the number of large displacement M engines, even HUGE displacement M's pulling every week at pulling contests I really don't think there's all that bad of a weak spot.

   I have seen enough H, Super H, 300, & 350 blocks with inspection holes somewhere along the left side of the block to say that those engines have a very mild conn rod problem.

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3 hours ago, jeeper61 said:

I have seen motors hydro lock and break a crank.

Could just have been a defect in the crank casting that finally let go.

these are forged steel crankshafts, not cast iron like the m +w cranks were.

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23 minutes ago, randy hall said:

these are forged steel crankshafts, not cast iron like the m +w cranks were.

Forged cranks can have defects as well that is why you should always have them magnafluxed on on a rebuild 

Testing by the the "ring" is not always fool proof 

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Broken cranks are not that common on old ms but it is not unheard of either. Just takes a bit of a flaw and after 70 years you have a big crack. Interesting think is most modern engines break them in a main saddle the motor still runs but vibrates like heck

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When I had my 450, I had it overhauled it in 2000. After they got into it they discovered that the crank was cracked in 3 places.

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