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valleybusman
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Dec 18, 2012, 11:04 PM
Post #1 of 7
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diesel crankshaft info
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I have alost the crankshaft in my GM 6.2 diesel. I find I can not find a replacement that isn't undersized.So my question is is there and way to find out if a cranshaft was turned right ?Also if it is turned down what should be done or have been done to make the crankshaft just as good as a new one ? How do I find out how the process was done right.Thanks
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Hammer Time
Ultimate Carjunky
/ Moderator
Dec 19, 2012, 4:08 AM
Post #2 of 7
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Re: diesel crankshaft info
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Turning down a crank is a grinding process. About the only thing that matters is the finished diameter and the finish of the grind. The thinner a Crank gets, the higher the risk is of eventually breaking but a small amount isn't critical. You will have to use undersized bearings, matched to the new crank size.
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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.
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Tom Greenleaf
Ultimate Carjunky
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Dec 19, 2012, 8:43 AM
Post #3 of 7
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Re: diesel crankshaft info
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6.2man: Just how to you lose a crankshaft? As HT said this is machine work. Another would be checked for all kinds of specs. Cranks kinda of share a mechanical DNA with the block originally used, the end caps that were torqued when it was line bored when new that you really don't want to get out of
order.
Depending on what happened that you need one could be real trouble now,
T
(This post was edited by Tom Greenleaf on Dec 19, 2012, 8:45 AM)
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Hammer Time
Ultimate Carjunky
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Dec 19, 2012, 9:28 AM
Post #4 of 7
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Re: diesel crankshaft info
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I would suspect he spun a bearing and took out one journal.
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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.
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Tom Greenleaf
Ultimate Carjunky
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Dec 19, 2012, 10:12 AM
Post #5 of 7
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Re: diesel crankshaft info
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Yes - I just can't see one falling out or being stolen or something
Total lifetime I've never spun a bearing. Heard of a few by folks who had just done something wrong with a redo all done and first start up was OMG right away.
Plain never heard of an existing working engine just spin one out of the blue. Seized engines just welded so who would know what else happened as those were declared dead weight and don't waste a dime or time as oil was so sludge or known overheated nobody is going to fix that. Connecting rods thru side of blocks, just on hard to diagnose cracked camshaft at an angle so it still worked but wasn't right. That was determined as engine had been wildly over-revved when stone cold. Not too many surprised that didn't have a warning or strange history...........
T
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nickwarner
Veteran
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Dec 19, 2012, 2:47 PM
Post #7 of 7
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Re: diesel crankshaft info
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If it spun a bearing you'll need the connecting rod too. by the time you do that much you may as well rebuild the thing. Seen more than a few that spun in the caps myself too. Not good. Had a cam bearing lock onto the cam of a Mack E-7 engine and spin in its bore. Only fix was a new block. Customer wasn't pleased with the price or the time it took to get one either.
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