The old ones are too worn down to clearly see the numbers. i’ll post a pic. I know that I had a head gasket leak because i already took the top end apart. New head gasket and valve cover gasket and pcvs etc. At that time the head and top end looked ok. I opened that in the first place because it was consuming coolant and oil looked milky and gooey. All the normal basic stuff seems ok so I went looking for that smoking gun. Did not find one 😏. This engine has 250k on it, and bearings were worn pretty bad. Still not the source of the noise but I thought I’d be making a mistake by not replacing them while it was open. Im hoping the ones I ordered will match the old ones. I planned to just measure and compare since I had no reference numbers. The noise never went away even with the engine warmed up. Oil pressure was good.

 

 

Can’t a bad torque converter sound a little like a rod knock? I’m not sure where Ive heard that before but since the engine seems ok, maybe its that?

 

Sounds like you need to plastigauge. Did you happen to check your flex plate and rule that out as the source of the noise prior to doing rod bearings? The rod bearings would have STD stamped on the back if they were standard size

 

maybe the bearings are incorrectly sized from the box. have heard of this before.

I would take my old bearings to somewhere that you can order new bearings of a different brand ie Clevite, and make a direct physical comparison on the spot.

I am no bearing expert, but from your photo, they appear to be incorrectly sized compared to the originals, nothwithstanding any wear

 

Ya definitely gunna plastiguage before and after and compare new bearings to old. The new ones are clevite/mahle and matched what the computer said they should be. Looking again at the old ones though, they do not seem to say std anywhere and kinda looks like it says .01 on one of them, which matches up with the undersized ones per the computer. I guess we’ll find out in the am when they arrive. Flex plate looked ok. I pulled the cover and rotated it a few times. I didnt see any broken teeth or significant wear but maybe. Im beginning to assume that this engine is fine and the problem is elsewhere. I havent touched the harmonic balancer, could be that i guess, idk. It runs, its just noisy. Crank position sensor?

 

HB should run perfectly true, if its the original, its up for replacement

 

What actually IS the year make of this xj?

 

OK I looked it up, clearly from your pics of the box, you bought the Clevite CB 960-40 bearings. The -40 means 40 thousands oversized from stock. For these to fit your crank would need to be turned down a whopping 40 thousands. Turning just about anything beyond 30 thousandths is never recommended anyway. So you started off with the wrong bearings. There are four sizes available in .010 increments. stock to 40. You want the stock, most likely.
Just hope you didn't pound on them too hard trying to get them to fit, that would ding the crank and well...not good.

 

First of all, measure the crank journals with a micrometer and compare your measurements with OE sizes. I've seen crankshafts turned .040 under on one journal to repair a spun bearing. Not a normal practice, but it is done more often than you think. DON'T ASSUME ANYTHING!!! Your main journal bearings should be about the same condition as your rod bearings. Also, if the head gasket was blown between cylinders #3 and #4, replace that time bomb head! You can use an aftermarket "Clearwater" head or an OE TUPY head. At this point, you're probably looking at an out-of-chassis rebuild. Just my opinion.

 

Absolutely. I had a buick V6 (ugh) once, I bought a 'rebuilt' crank. After 5 months it snapped in half getting off the highway in Marcy. I took it to a mechanical engineering firm, and a PE looked at it for 2 weeks. He told me under the microscope he could see where someone had turned it way down and welded it back up on the #3. Which restored the journal diameter, but the forces transmitted through the crank do not go through the weld, they go through the original steel. So it was weak there even though the weld restored the journal diameter, the force was still only going through the original diameter, which was cut way out of spec. Ill never forget that sound, everything was fine then "KLINK" and red lights on the dash.

 

Ya so someone has been in your engine before. The bearings you took out are .001. The ones you are trying to put in are .040.

Looking at the part number on the box the -40 at the end means they are .040 bearings. You will need bearings that end in -1 if you want the same bearings that came out of the engine.

Are any of the rod caps super dark, like almost black and/or darker than the others? I have a feeling it may have spun a bearing at one point and someone threw in the .001 bearings to cover it up.

 

Its a ‘98 ZJ 4.0...hard to tell if one had spun at one point or not. I actually thought I would find one that was about to go. The crank is pretty smooth but maybe thats because its been worked on. The bearings were worn but nothing catastrophic. I’ll take a look today to see if any caps are darkened. I figured I was gunna hafta take the head back off. If I do, I’ll change the head out. You guy’s suggestions have been very helpful!