Main Bearing opinions please

I have a 97 cherokee with the 4.0 engine. My oil pressure starts out at 40 pounds cold and then drops to 10 pounds once it's warmed up and the engine knocks. I went to a mechanic and wasn't surprised to hear that the bearings were bad. He wants to just replace the engine with a rebuilt one which is probably the ideal thing to do. Problem is that I can't afford a new engine. I'm wondering if it would be a good idea just to have the bearings replaced. The engine has 117000 miles on it and doesn't use or burn a drop of oil between changes. As a matter of fact the oil looks great when I drain it during changes. Also the spark plugs always look great when I change them, sometimes I feel silly installing new ones they look so good. It still seems to run great other than the knocking when it warms up.

Mines had a mild knock at idle for the last 50,000 miles. I run 20-50 weight oil, it bumped up the oil pressure.

Do the bearings. But the knock is rod bearings, not mains. The main bearings on 4.0Ls rarely need replacement. However, once the pan is off to do the job, it's not much more work to replace the mains. Do the rear main seal while it's open, too.

I'll second doing the rod/main bearings and rear main seal.

I had that done on my '92 at 170,000 - the dealer I had it at for an oil change (was convenient) didn't even really want to put in a rebuild - said it wasn't worth it (dealer mechanics seems to get skittish when faced with an older vehicle needing a big job - can't imagine what they'd do to me if I brought in my 21-year-old Omni for an oil change and a vacuum system renewal, probably run the other way real fast ). That got me to thinking that I should snap up one of the current ones (was summer of '01, so the last of the XJs were on the lots). I ended up buying a TDI and having a local shop nearer to home do the bearing job on the XJ.

Now I have what I consider to be nearly the ultimate vehicle combo - the 40+mpg diesel commuter sedan and the XJ for hauling/wheeling/snow duty.

Your engine has a lot of life left in it - find a good shop to to the bearings and seal (sounds like the guy you took it to isn't too interested), and keep spinning that odometer.

Rob