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Discussion Starter · #1 ·
so i need to replace my rod bearings, it had been rattling now for a few days and i just got to it...the crankshaft doesn't look or feel worn much for a almost 200k engine. should i use standard size bearings or oversize or under? and what would that do?
 

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I would mic the journals, compare to standard, and them decide which bearing to use, then I would also plastigage with the new bearings. I would also mic the mains as well.
 

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Discussion Starter · #3 ·
I have just put in a new standard bearing and it has no play...
 

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Discussion Starter · #6 ·
the crank isnt to bad, and the bearings are all in one part, just a lil worn....do i need a new crank or will oversize bearings be just fine?
 

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Discussion Starter · #7 ·
and would anyone have what the allowed clearance is for the bearing to crank shaft? i have plastigauge and want to be sure...
 

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If you are interested in doing this correctly, you need to do a little studying on engine rebuilding practices. You would be wise to get ahold of the factory service manual as it has some good info on this. Looks and feel are not the proper inspection criteria.

Preferred rod clearance is .0015-.0020"
 

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If it was knocking HOWEVER SLIGHTLY the big ends of the rod are most likely now out of round and new bearings wont fix anything and oversized bearings may be so tight you will do more damage. Like DREDnot says you cannot tell by look or feel.
 

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If it was knocking HOWEVER SLIGHTLY the big ends of the rod are most likely now out of round and new bearings wont fix anything and oversized bearings may be so tight you will do more damage. Like DREDnot says you cannot tell by look or feel.

This is very true, you need to pull the crank out and take it to an Auto Machine Shop, have them turn it to the next usable size and buy the bearings for that size, mains and rods alike. then reinstall it all with a new oil pump, timing chain at the least, but if you have 2K mile on it, I would think you should bore and new pistons and rings, cam, lifters and bearings and rework the head.
:rip:
 
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Discussion Starter · #11 ·
Ok thanks, I did alot of sizing and everything was fit within the standards in the jeep manufacturer manual, the crank was 02.093 which fits the book, and the bearing to crank is .0016, the okay thing that has me worried is the side of the rod when attached to the crank has just over the recomend spec in the book...(forgot what the technical term for that is)...
 

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Discussion Starter · #12 ·
How it all started was I rebuilt the head and all, and I forgot about the MAP vacuum line, and it was burning some oil...during that the oil level must have got kinda low and hurt the rod bearings, I put no more then 30 ish miles of light driving on it...
 

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If you starved it for oil and damaged bearings the crank will need polished at minimum..

If it didn't damage the bearings you may have heard lifters noise and not a rod knock.

If you are gonna change em go back w the same size that are in it now and hope for the best.
 

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I wouldn't get too excited about a LITTLE extra end play on a rod journal
 
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