SlickXJ

Hi everyone. I will try to make this pretty short and to the point. I recently replaced the engine in my 96 XJ with a low mileage one. While I had the low mileage one on the stand, I decided to do the rear main seal. I completed that no issue, torqued it to spec (foreshadowing), and put the low mileage engine in. Note, after doing the RMS, I never tried turning the crank by hand to verify it wasn't bound up, which was a HUGE lesson it seems.

Anyways, the XJ sat for 2 weeks after I put the engine in. I went to turn the flywheel to match up to the TC and, uh oh, it won't spin. I knew it wasn't bound on the TC snout because for one, it went together like butter, and two, I could spin the TC by hand through the starter hole. I though my shoulders were just weak and I needed to try turning it from the crank bolt. Still won't budge. Rather than snap my crank bolt trying to turn it over, a light bulb went off in my head. "Did I over torque the rear main cap when I did the seal?" I had written down the spec as 85 ftlbs. After checking with the powers that be again, I found it it's 80 ft lbs. To take out the error of my torque wrench being off, I got some plastigage to check bearing clearance the second go round. Although it sucks to do with the engine in, I thought, well it's not the end of the world. I'll just raise the front end up, let the axle hang, get the oil pan out and redo the torque. After breaking the rear main cap bolts loose, I decided to try and spin the engine by hand before going any further to verify that was the problem. Taa-daa, it spins, but noticeably harder than I think it should. I decide to investigate and actually take the rear main cap completely off to inspect it. What I found made my stomach sink. What once was a perfectly good main bearing now had a small dark rust spot on it. After cleaning it off with my finger nail, it revealed what you see there. The pitting is about the size of half a pinky nail, but nonetheless there. The shiny edge that goes around the perimeter of the pitting is actually ever so slightly raised. My guess is the rust got under the tri-metal layers and started delaminating/rust-jacking it. Luckily, after spinning the crank around with the cap out, it took no damage from this (pitting, scoring, etc). I took some 3000 grit crocus cloth and using it wrapped on a Q-Tip, tried to slightly whittle the raised bit down. Holding the bearing up to a light now show that raised edge is almost flush with the actual bearing surface, but I'm still super leery of reusing it. It's one of the .001 undersize bearings, classically annoying to find. Luckily, I found some Mopar ones on Summit for $24 a pair. Here are my questions:

- Do I use it as is because this bearing is mated to the crank? (100k mile engine)
- Is it ok to just replace a single main bearing and leave the others alone?
- Do I get the other half of the bearing out to check if it's a .001 undersize or Standard size, order accordingly, and put new bearings in just that main?
- Do I put .001 undersize bearings in both sides regardless since it's not a new crank and could probably use the extra tolerance tightness?
- Is it ok that I have the engine open to my garage (oil pans off) while I wait for parts to come in? Is there anything I should do to prevent any surface rust from forming?

So much for a short and sweet explanation lol. As for how this happened, I'm really not sure. Before installation on the stand, I wiped the main cap and bearing clean, put the bearing in the main cap, then did a light coat on all exposed surfaces with new engine oil and reinstalled. Engine assembly lube likely would've been better, but I didn't have any and I figured engine oil is better than nothing and it's not like this was a rebuild.

As a final note, there are no other engines for sale within 3 hours of me and I do NOT have the money for a rebuild.

Here is the bearing I'm looking at: https://www.summitracing.com/parts/m...okee/year/1996

bluejeep2001

Kind of tough to decipher the whole story but 5 ft lbs on a bearing cap will NOT crush the bearings and keep the engine from turning. Once those caps bottom out, they don't get any closer until you overtorque by a ton. Did you prelube anything or just install the motor as an assembly. Now if your bearings are not the correct size for your journals...now thats a different story...also if your off by only. .001..that should not lock you up. Its almost impossible to mike the crank journal while its still in the block..i did not see if you plastigauged that bearing...do it it will let you know the clearance. Contact me if not sure how to do it...easy and takes 5 min let me know how else i can help...built 3 strokers

280ezrider

I agree that it's almost impossible to mike the crank journal while in the engine, but I would at least try. Also a dial gauge could be used to at least check for out-of-roundness of the same journal while a helper turned the crank. This reading could provide an indication of what to do next. Obviously, the amount of room is not ideal, but it's worth the effort. In the end, I would not feel comfortable reusing that bearing.

country2

Is it a possibility the rust was caused by your finger prints? Anyway...Plastic gauge and assembly lube! I learned my lesson back in the 80's while going to school for a automotive tech. We have a V-8 motor to pull apart, reassemble and run it. Little did me and my partner know that the teacher gave us a motor where the caps were incorrectly stamped...long story short we did not use plastic gauge just went by the numbers on the caps lubed and installed and motor was locked down. had to remove the caps and gauge them to find the best fit...lessoned learned!

bluejeep2001

Here is one of the things that don't make sense...if all you put in was a rms....its rubber so it can't stop anything. 5 or 10 extra foot pounds wont damage a bearing. There s very little steel in a bearing, its mostly copper and tin so it shouldn't rust...ever. If you didn't change the bearing size then do the plastigauge reading on it...should be around .002 clearance. If its ballpark then replace with the same and then take ALL the bearing caps off and brush on a good bit of assembly lube to the bearings and journals where you can get to them. Unless you loosen all the caps anyway its very difficult to replace the bearing on the block side of the crank if the crank doesn't have any "wiggle" room. Oh yea while the last cap is off super lube the rms so it doesn't run dry and heat the seal . You might have to do all that then pull the distributor when its all back together and prelube the crank and rods for a while...makes startup easier. I bought a used distributor on ebay for 10 bucks...knocked off the cam gear and installed it into the block...now you spin it with a drill motor and it pre oils everything.Spin the engine a few times while your doing it and everything should rotate freely...at the risk of the obvious....take out the spark plugs while turning with the wrench on the crank bolt

bluejeep2001

One last thing...hopefully. Take the lower coverplate off the tranny bellhousing and loosen the bolts that hold the flexplate to the torque converter..that might not be seated correctly and it might be binding. Spin the engine a few times by hand / wrench and then retighten. The "holes in the flexplate are slots so make sure the bolts are against the side of rotation and not in the middle or reverse end of the slots. If all the bolts are loose you can rotate the flexplate or grab a bolt and move the torque converter and see what I mean. The bolts should be against the left side of the slot looking back towards the tranny...good luck

97grand4.0

With a new RMS in there, I would guess that it got squeezed into the journal space or it twisted and is locking up the crank that way. Also may be the wrong seal. Take the rms out and try again.

A better guess is the replacement bearing. You keep saying .001 undersized bearings. Don't you mean .010 Oversized ? Oversized bearings are quite the step to take, normally you wouldn't do that without removing the crank and having it machined down .010 first, otherwise its going to seize especially if you don't plastigauge it. Plastigauge will tell the whole story, do this instead of pulling the crank or trying to put a micrometer on it.
I don’t think bearings come in 1 thousands increments normally but I could be wrong.
Anyway if you left the original bearing in, and just did the seal, Id say its obvious you messed up the seal installation somehow and it's binding in the bearing, or, maybe something contaminated the bearing like sealer or dirt. If it plastigauges ok, put it together again and spin by hand.

SlickXJ

First off what I will say is this engine came out of another 96 XJ I bought whole and got running after the PO let it sit for almost 2 years. So I know it runs at the very least. I don't know the oil pressure because I don't have a mechanical gauge and it just had the dummy light on the dash, no gauge.
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I prelubed with new engine oil since I didn't have engine assembly lube at that time. When I say .001 bearings, these are factory .001 undersized bearings which is stamped on the back, meaning the ID is thicker than STD. From my understanding, they used either STD(standard) or .001 undersized bearings to compensate for the manufacturing process. Also, oversized bearings would be used in a situation where you have your main journals line-bored because the OD of the bearing is larger while keeping a stock ID. Undersized bearings are used when you need a smaller ID on the bearing because you took material off the crank and you need to compensate with the bearing. Here's a post from a NAXJA thread on this:

"Pistons and rings are "over"sized -- bearings (rods and mains) are standard or "under"sized. Nobody has a crank that's bigger than standard.

The aftermarket sources are going to have the .010 and .020 undersizes because when a machine shop has to grind a crank, they go to one of those as the "standard" undersizes. (Just as pistons come in standard and .010, .020, and .030 over). The .001 and .002 undersize shells are dealer only, as far as I know."

The bearing was perfectly fine when I initially did the RMS. I didn't spin it by hand after assembly, but I'm guessing that somehow I contaminated the surface of that bearing during assembly.

I was wearing a fresh set of gloves when doing this job. Changed them after I got the oil pan off on the stand. I had to have contaminated it somehow though, it doesn't just form, especially since I coated it with some engine oil prior to assembly.

Correct, this is the .001 undersized bearing it came with from the factory, running perfectly fine before I did the RMS and looked in perfect condition as I did the RMS. If I were to replace the bearing, I figured I'd have to slightly loosen (2 turns per bolt) all the main caps anyways to be able to slide the block side bearing out anyways. I have the dizzy from the old engine I can modify anyways if I do go the prelube route.

I never even bolted the the TC to the flexplate! I can spin the TC by hand through the starter hole in the bellhousing, so I know it's not the snout of the TC binding on the flexplate/crank. But I see what you're saying. Loosen all the flexplate bolts, spin the crank clockwise, then tighten so it can't start wobbling. Makes sense.

Just test fitting this bearing with assembly lube on it and torqued to spec the crank spins beautifully. My only thought is a lack of lubrication. Basically like the engine oil wasn't enough since I let it sit for 2 weeks after I put it in. And nope, I legitimately mean .001 undersized bearings, stamped right on the back of the bearing. Seem my response from above about the bearings. And considering everything I've just said, I would say it's obvious the main issue was a lack of lubrication in my assembly and the fact I let it sit for 2 weeks without spinning it over or anything before I could work on it again. I have learned to NEVER touch bearing components unless I have engine assembly lube on hand or I'm going to button it up the same day haha!

All these responses bring me back to my original questions. Do I spring for the factory replacement .001 undersized bearing I linked in my first post and hope the broken-in crank and a new bearing cause no issues? Or do I hope the oil and zinc fill this cavity(I call it a cavity but it's not deep) and give me the 2-3 years I want out of this engine while I have a machine shop do a rebuild/stroker build out of my old engine.

I know no one can be certain if I'd get 3 miles or 30,000 miles out of reusing a bearing like this. I've talked to a couple older engine builders and they basically tell me I have a 50/50 shot of either method working. They've seen shot bearings go 40k until the person had money for a rebuild, and they've seen shot bearings tear an engine to pieces in 50 miles. Same thing with putting in a replacement bearing. Could go well, or could explode in short order. I believe since there was no knock(aka crank should be fine) on this engine and it was a lack of experience mixed with bad luck/timing that caused this bearing pitting, if I just replace bearings on the rear main then I might get lucky to get the 2-3 years I want.

Input?

SlickXJ

Alright, update for everyone.

Since the engine sounded healthy before, and the crank looks/feels good, I ordered a 83507080AB from the dealer. $34 plus tax. I will use ample engine assembly lube, as well as prime the oil system with a spare distributor I have and turn the engine over by hand to coat everything. I will also be using plastigage to confirm clearances before final assembly.

Part should be here in about a week. Will update once the job is done.

bluejeep2001

You have not stated the results of the plastigauge...it will tell you if you are too tight or good or too much clearance...then there is no guessing on your bearing size...

SlickXJ

Not sure why I'd be plastigauging the bearing that came out. The bearing states what size it is on the backside of it, so I just ordered a new one from the dealer. I will be plastigaging before final assembly. I believe I communicated my issue poorly or I'm misunderstanding your perspective. Very shortly summed up:

- I got XJ #2 with a good engine (I drove it around and it felt and sounded good)
- Did RMS on XJ #2 engine while it was on the stand (bearing looks great at this point) and swapped the engine into XJ #1
- When buttoning it up, engine wouldn't spin (sat for weeks after initial swap)
- Took off RMS cap and found a big spot of debris where you see pitting
- Cleaned debris to find pitting

Wanted to know what my options were short of rebuilding or getting another engine. I concluded I could either:
1. Send it as is after making sure pitted area wasn't above bearing surface (if not it'd likely score the crank)
2. Buy a replacement pair of bearings to redo that single main
3. Buy a set of main bearings and do them all

After deliberating with many people, I decided to go with route #2 as a low-buck "it'll probably work but you're mileage may vary". Sorry if I confused anyone with how I delivered the information I had.

EDIT: The bearing should be in by Tuesday so I'll update as soon as I get it in.

bluejeep2001

The reason to plastigauge the original bearing was to check your clearances before you bought bearings with the same clearance.. That little tiny irregularity cannot possibly stop an engine from turning. Engine bearings need lube between the bearing face and the journals. If your rods and mains don't have a good layer of assembly lube or recent engine oil...they will rub or drag. If you dont get oil into all those bearings you have wasted your time

awg

I think I would personally at least loosen off all the mains, one at a time, and see if the crank turns

If not, you know it is likely the seal is somehow jammed up

the only caution would be if you think the bearings lack lubrication (in which case more is needed)

I would not just fit a single new shell and try turning the crank, without doing the above

maybe I have mis-read what you have or intend to do

bluejeep2001

Have you gotten your parts yet? Any luck?

SlickXJ

Yea, I think I miscommunicated my problem and what I intended to do. When I can explain it in person it makes more sense, hence why a couple machines shops told me my plan would probably work.

Yes I did. Put in the bearing, plastigaged showed .002 clearance which is ideal spec. Buttoned everything up and primed oil pressure. Started it up and it idles at about 40psi oil pressure when it's -6C outside with fresh T6 5W-40. Haven't taken it for a drive yet cause I need to put my new set of tires on but I ran it for about 30 minutes at varying RPMs while checking for leaks. So far no leaks and it sounds fantastic.

This is the replacement bearing plastigaged.

I don't know if I didnt mention it, but I measured both old and new bearings before install and the new one was bang on. I didn't just buy a bearing on a whim and slap it in. If anyone has any questions about what happened or what I did, let me know and I'll try to answer them clearly 😂