Here's a pic of the main bearings from #2 through #6 where #2 is at the bottom of the pic and # is at the top. You can see the worst is #6 and I'm curious about #3. What is that thing wrapped around the sides of #3. Is that spacer suppose to be there or is it a "fix" of some kind.
Mike, does your theory still hold true? Does this look like it would be caused by #2 or is this engine just freaky (nice cylinders without crosshatch with bad bearings)?
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If this was local to #2 I was building up to fixing this myself (honing, mic'ing, replacing bearings, replacing rings) but now I don't know.
That thing wrapped around #3 is the thrust bearing, which controls crankshaft movement fore and aft.
If you are looking to just put bearings in, go buy a set and run a plastigage check on each main, and that will tell you if the crank is worn. All of the wear that I see isn't unusual for high mileage. It is just time for some overhaul work.
The easy question first. The #3 bearing is different because it is a thrust bearing. This keeps the crank from moving axially. There should be a spec for crankshaft end play in your manual. It is normally about .005 to .010" depending on the engine manufacturer. The surfaces that the bearing rides against on the crank should be checked for wear if you are going to reuse it.
Nothing really stands out as a big problem with the bearings, but they probably have a lot of miles on them. It is normal to see a different amount of wear from front to back on engine bearings. The oil is fed through the crankshaft, so some of the bearings take longer to get oil than others. I'm not real sure on the oiling schematic for the 258, so I may be out to lunch on this one.
To me, it just looks like that puppy has seen a bunch of miles. Wear at the bottom center of the insert (as opposed to the sides) is normal as the clearance increases, wear one one edge or the other is common as the rod side clearance increases with wear. It's fairly common to see the thrust bearing in better shape as it usually gets a little more lube to account for the thrust surfaces having to be oiled by the same feed as the journal surface (more oil flow). You need a full rebuild, but I don't see anything that would be a real issue unless the crank needs grinding below tolerance. I think you've got one well used engine and you need to spec it out to see what needs machine work (which will dictate, in large part, what parts need to be replaced). If you don't need new pistons (clearances good, etc) then it's probably worth looking into having the crank ground (if it needs it), throwing in new inserts and rings and pressing on. You'll have to determine by hard numbers just what shape it is really in and go from there.
Side comment: the pictures you have posted have been pretty darned good. Nice job on those.
These are severely detailed, about 175k each but still not too bad with dial up (what I have).
Main Bearing #2
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Main Bearing #3
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Main Bearing #4
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Main Bearing #5
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Main Bearing #6
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Don't know if added detail would sway opinion or not :-)
What confuses me about this whole thing is the condition of the cylinders and the compression readings. If this engine was as worn as you all say then shouldn't there be a ring ridge on the cylinders? These guys (visually) are as straight as an arrow. Wouldn't I have much poorer compression than I have?
Perhaps they bored the cylinder and then put the old parts in it from the previous engine? Confusing.......
You are in the classic case of ok, just what was done to this 'refurbished' engine before you got it....
The top end seems fine with 'excellent' compression except for the one cylinder not firing. No wear marks with an overbore that some folks do to increase the cubic inches for an 'increase' in power. You know 'hey 'my' engine is bored out to a 4.5 L' or something. Like folks with strokers make either a 4.7 or a 4.9 according to how much they overbore the pistons.
They could also have put in the ring type that call for a smooth bore, I think the hard 'power' rings or something.
The bottom end looks like it either wasn't touched, or it was all done
10 10 under and got damaged somehow. That thrust bearing usually gets the most wear and in your case, the sucker seems new.
You have no factory codes on the block to indicate a factory under crank, so the crank 'was' changed for sure and a 10 10 one is excellent for a turned crank. I see lots that are 20 to 40 under after a turn.
When gas gets in the oil and/or washes down one cylinder, it cleans all that hard flaky varnish like stuff off everything, then you have a spark for a while to build up more, then it gets washed down again.
All these little pieces of hard crap can get in between the bearings and score/gouge the crap out of them like you see in the photos. Carbon under heat and pressure turns into diamond eh?
So if this is just a case of gas wash doing in the bearings, then a stock 10 10 or whatever number is on the back of the main bearings put in carefully should be all you need.
This can be checked with plastigauge. (do you know what we mean here?)
A micrometer can also be put on the journals and turned around to check if the crank is still true or round. My guess is it is still ok, I think you caught it soon enough because those bearings aren't destroyed, just worn.
Let me see if I understand this correctly. The first order of business would be to Plastigauge the journals with New Bearings to determine if the Crank needs to be turned or is within spec. "If" it isn't, then all the bearings would need to be returned, the crank would need to be turned, and new bearings would be used?
Please expand on this process.
Additional Questions:
What other parts should I be looking at for wear? Are there are other bearings at the front and rear which also need to be looked at for wear?
What about the Top Sides of the Main Bearings. Should the tops of the main bearings be replaced and if so, how are they removed? Will the Crank need to be removed?
Remember, I'm planning to bolt down the 4.0L head on this puppy. Will it be able to take it?
Too bad my big tree and driveway are so far away. ;-)
The crank will drop enough to push out the top bearing halves. Just note where the dimple is and push from the other end. They come out pretty easy. You will have to support it so it doesn't damage the tranny nose piece or unbolt the tranny and pull it back so the crank can drop right out.
Man, trying to call the crank while it is still in the engine is really difficult. Even if I had it in front of me, it would be really difficult.
I 'think' I would get my hands on a micrometer and try to run it around and across the crank journal faces to try and see if it is still even for size and round.
I usually get them out and just take them in to a machine shop. They can tell really fast if you can just re- bearing it or if the crank needs a turn. I know pulling the tranny back is a bugger, but I would recommend you do that so the crank just comes out.
You need to pop one of the main bearings out of it's cap to see what size it is. If it only a 10 over like the piston rod one, then a small
10 or even a 20 turn can be done on the crank still if needed and the machine shop will give you the 'right' bearings for the turn.
Otherwise you would have to plastigauge the crank in place and find some place that will accept the 'used' bearings back in trade for a bigger size. If you do need a bigger size, the crank will have to come out and be turned anyway, you are correct, they don't make bearings 0.001 sizes, only 0.010's....
I would also have the ring type identified to find out what kind of finish is required on the piston bores. If smooth, then I personally wouldn't touch them, I would just put the rings back on the one piston and put it back.
Then you could end up with an over-bored 4.2 with a 'new crank and bearing set' running a 4.0 injected head... Could have a pile of power...
So you must have had really shitty oil pressure eh?
Did you notice an oil pressure drop recently or has it been low since you owned it?
Well, I guess, if not anything else, this unique position has exposed me greatly for learning which is what I wanted when I bought the jeep. I just wasn't expecting this much :-).
When I had the compression tested by the local mechanic I also had him test the oil pressure since my gauge was showing low since I bought it (10 to 20 psi if I remember correctly at highway speeds). Anyway, when the owner called me on the phone with the results he told me the mechanic said it was
45 psi. Then when I went to pick it up the owner said it was 40 psi. It's amazing as when I brought the jeep to him and told him just what I wanted which was all test results recorded they said yes oh yes, we can do that. When I went to pick it up the owner, not the mechanic, scribbled the compression on the page. Nothing about the oil pressure so I just have the verbal record. I have a brand new Autometer mechanical oil gauge sitting on my kitchen floor ready for the next engine or this one rebuilt.
I have checked out a lot of vehicles over the years for friends before they buy, my wife thinks I should start a business at it...
I always recommend someone go to a mechanic 'they' know and spend the $75.00 or whatever an hour costs to have it gone over. That can be the best money ever spent on it.
Low oil pressure screams worn crank bearings.....
Buying used with unknown used parts in it is just plain a crap shoot. Sometimes you win on used stuff, sometimes you lose...
You really need a pro to look at things in person at this time.
The bores could be perfect for the rings and the bearings could maybe just need replacing with the same size to get another 100K out of the engine if the FI system is tested working right...
We can be talking a couple hundred dollars in parts vs a rebuilt block. Your block is already bored out with I suspect 'performance' rings in it and a quickie on the bearings might be all that is needed.
It sure is a fast and hard learning trip though isn't it?
One gent I met from this group had a seriously screwed up 'rebuilt' engine. Turns out he lived literally right around the corner from me in about 5-10 minutes walking distance.
He was a computer tech that had only touched a wrench once. Well, I helped him rebuild his engine in an unheated garage between Xmas and New Years at -25C. LOL. Man did he ever learn fast....
There was a good thread here about that. 'Rebuilding the Rebuilt from Hell' or something like that. Man it was nasty, the rod caps weren't even on the right rods! If you look at the end of the caps, they have numbers on them. The piston side also has numbers. They are supposed to match!
"Only touched a wrench once"... and it's still frozen to his hand!!!
Hey Mike, would you be interested in a trip to London to help me with a lift install on my XJ? Just tossing the idea around in my head... You could bring your wife and the girls could wait on us hand and foot... bring us beer and sandwiches (wishful thinking), I'll pay for your hotel and gas, we'll feed ya and we can get greasy and frustrated together! I have an electric impact, every size in sockets and wrenches, pry bars, big ass 4' bar etc.. the only thing I don't have is torches. The sooner I get off my ass and install a lift, the sooner I can join you on a bush run. Times like this I wish I still lived in Oakville... access to a shop etc. my friends here are all pen pushers! LOL. Let me know if you're interested and we can discuss it further.
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