4.0 Engine Rebuilders - Please Help ....

As some of you have read, I've been trying to replace the rod and main bearings in my 88XJ w/174K for two weekends. One weekend was spent just trying to determine what size bearings I needed. I finally realized that my engine was manufactured using .010" inserts for all the rod and main bearings.

My concern lies in that the next size available insert jumps up to .020" should replacement .010" insrts not do the trick. In fact. after replacing the rod bearings with new .010 inserts, I ended up being .001" over the maximum tolerance (using plastigage) stated in the FSM. I'm afraid if I jumped up to a .020" insert, I might end up binding the bearings.

I'm still waiting for replacement main bearing inserts (.010") to arrive at the parts store. I've measured the clearance of the main bearings (with original worn inserts) using plastigage. Each bearing is .0015" over the maximum tolerance listed in the FSM. Hopefully, new inserts will bring the clearance back into tolerance.

What I would like to know is, with such a large size difference between sequencial insert chioces, should I move up to the next size insert, or would I be better off being slightly over the maximum bearing tolerance?

P.S. This is my 1st time working with the guts of an engine, so any advice or hints will be appeciated.

Why not just have the crank turned and get matched bearings from the machine shop?

With the bearing on you want about 0.001 to 0.0015 for oil clearance. So, if you currently have about that much or just a little over install replacements that are the same as the originals. These should tighten stuff up just a tad.

lunghd said:

Why not just have the crank turned and get matched bearings from the machine shop?

Click to expand...

Bender, This is what I'm hoping for concerning the main bearings. However, the rod bearings have a clearance of .004" after installing replacement inserts. The next size available insert is .010" larger, which mathamatically, should place me over the minimum clearance stated in the FSM by .007". Thus my dilemma. Seems like I read a thread somewhere stating that a little to big would be better than the other way around.

Lunghd, that would probably be the ideal choice if I had the time and resources to do everything associated with removing the crankshaft. Unfortunately, I need to get the XJ back on the road. This may be a good summer time project.

In a related question, when lubricating bearing inserts, should just the journal side be lubricated, or both sides (realizing the FSM states that the bottom rob bearing insert goes in dry)?

You will have to either pull it down and have the crank turned, buy a crank kit, or put it back with new -.010 bearings....you have no other effective choice...

If it had standard bearings instead of -.010 bearings, you CAN get -.001 bearings for use on slightly worn but good standard size cranks....sadly they don't make -.011 bearings.

If it is worn beyond spec, chances are the journals have out of round and/or taper anyway.

If there is no way to do a proper job now...put it back together with new -.010 bearings, drive it easy and plan the real repair...

* Inserts, install with the backside dry and CLEAN...lube bearing surface and crank....don't forget to lube the rodbolts/nuts before torquing.