bluejeep2001

If I understand you, and im not sure ...if you put an undersize on cyl 4 bottom, you must put the same undersize on cyl 4 top. And if cyl 5 takes a standard on top then, the bottom of cyl 5 must also take a standard. You can mix and match positions...1-2-4-5 undersize in entirety (undersize half for top and bottom) .AND have standard it top and bottom of 3 and 6 But you CANNOT have an undersize and standard on the same cyl/piston

Spencer_P

Hmm, FSM states mixing sizes within a certain range is perfectly acceptable so long as they are consistent (all undersize on the upper, all standard on the lower). Not only does the FSM say so but the engine has mixed bearings that I'm 99.9% sure are factory.

Spencer_P

I'm unable to source a set of .001" undersize crankshaft main bearings. I've found Crown Automotive J8133680 on Amazon and Mopar 83507080AB on Summit both are just a set of two and do not include the thrust bearing. Any help with that search would be appreciated.
Also, I found another post about a 93 ZJ, and the bearings have the same part number as mine and are dated 8 92, which to me confirms my bearings are original. Why they vary so much I'm not sure but maybe that isn't too uncommon, I've never been inside another 4.0.
I'll post another update in a day or two when I've got time to look over some measurements I took last weekend.

Spencer_P

I believe this should include all measurements taken and bearing sizes that were removed. These are the best measurements I could get with a digital bore gauge and a micrometer. Given my measurements, FSM 9 - 62 says to mix standard and .001" for the connecting rod bearings, which is what I removed so I think I should be good to do that. The confusion comes in on the crankshaft main bearings. Given my measurements and FSM 9 - 65, my main bearings should be #1 - .001" & STD, #2 - .001" & .001", #3 - .001" & .001", #4 - .001" & .001", #5 - .001" & .001", #6 - .001" & STD, #7 - .001" & STD, which does not match the factory bearings I pulled out.
Two things I do not understand:
1) I don't see mention of using the bore measurement to choose the bearing size which I would think would go hand and hand with the journal diameter measurement, and since my main bore measurements are on the high end of spec and my connecting bore is .0004" over I'm unsure if I need to factor that in.
2) What I'm reading in the FSM in regards to main bearings doesn't quite match the bearings I removed, so do I replace them with the same size I removed or follow the fitment chart?
Regardless I will need to source .001" crankshaft main bearings which I have been unable to do.










Again the help is greatly appreciated! I really need to get this project wrapped up so I have something to drive while I give the daily some attention.