WJ bottom end rebuild crank won't turn - JeepForum.com
 
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post #1 of 8 Old 08-02-2019, 09:38 PM Thread Starter
Anthonyc24
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Currently I am in the process of rebuilding the bottom end of the motor 4.7 v8. The previous owner took it out and ran it without oil causing the number 6 bearing to wear down and clog the oil port. After awhile he noticed a slight knock so he stopped driving it and sold to me for cheap. I took the engine out flipped her upside down and started digging into it. We went all the way down to the crank and found the cause of the issue so we replaced everything down there rod & main bearings, polished crank, new seals, and oil pump and tube.

Now while on the install we lubed everything up and tq'd to spec but now we can't turn the crank. I put in there standard size rod bearing and main bearings And platigaged everything was good but still wasn't able to turn.

So we started untighting them and making them just hand tight to see if that helped. It did we got down to 2 rods being tq'd the rest being hand tight and it turn. But no matter what as soon as I tq any other rod I can't turn it. It's thrown me and him for a loop.

Note: My buddy is a ase certified tech 😅😅 and been working on engine since he was a kid. so if he don't know I'm hoping someone here does cause I certainly have no clue.

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post #2 of 8 Old 08-03-2019, 07:00 AM
V8GCZJ
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Sounds like the crank or connecting rod is bent.
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post #3 of 8 Old 08-03-2019, 08:55 AM
DesertRata
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Agree with above,




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post #4 of 8 Old 08-03-2019, 09:06 AM
texomakid
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WJ bottom end rebuild crank won't turn

Iíve never rebuilt a Jeep but weíve built a couple dozen SBCís and Iím with the others. Bent crankshaft or rod? Somethings in a bind.

Iíll also add even though weíve used plastagage on many motors Iíve seen a few instances where it wasnít very accurate compared to using micrometers.

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post #5 of 8 Old 08-03-2019, 10:38 AM
Newtons3
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Loosen the mains 1 at a time and turn the crank. See if you can isolate the problem. Move to the rods. If the crank won't turn, yes...it could be bent, I'd suspect something else. Did you check the big end of the rods for size in 3- 6 positions to make sure they are round? Plastiguage is OK but by no means guarantees a good fit.

If it turned before you tore it down, and now won't, something you changed has caused it to bind. I would suspect the new bearings are binding somewhere. ASSUMING (never appropriate) a correct install of the mains, I would suspect an egg-shaped rod big end. My next guess would be a stacked bearing or one trying to stack.
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post #6 of 8 Old 08-03-2019, 06:15 PM
jay-h
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Probably you checked, but are you sure the endcaps are on the same rods they came from?

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post #7 of 8 Old 08-04-2019, 11:27 AM Thread Starter
Anthonyc24
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Hey guys thanks for the ideas. I just went through and tried to isolate on the mains but nothing worked. I tqed all the rods and then untightened each main one at a time but it was locked up. I'm going to at this point take the bed plate off and measure each rod.
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post #8 of 8 Old 08-05-2019, 04:39 PM
Don Stamper
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Bet you may have to get the rod big ends resized.
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