3.9 main and rod bearings - Land Rovers Only

BIG DADDY · 10-04-2007, 03:54 AM

I recently purchased a 90 classic. the odometer shows 169,000 The motor sounds great on startup and at full temp. No smoke, wrap, clatter what so ever. I don't have any long term history other than the "littlle old Lady" only drove it down hill..... My question is has any one ever changed main and rod bearings on one of these high mileage motors without any crank or rod work?
This may seem like a silly question....... I am new to land rover and have not seen any other posts other than "rebuilt my motor" or "changed my head gasket" I do not at this time have a compelling reason tho drop the pan, just thought I'd pose the question.

Leon
1990 Classic
2000 Saleen S281
1987 K75s

TerryS · 10-04-2007, 05:16 AM

I have. I used Federal Mogul bearings, they're a known quality supplier. As long as you plastiguage when setting, and have miked the crank journals.
How are you planning on doing the mains in the car? The rear main will be pretty hard to roll out with the crank hanging off the torque converter. Good way to break the pump on the ZF.
Unless there is evidence of copper showing on the rod bearings, I wouldn't bother to do it till you're ready to pull the engine and do the whole bottom end properly, i.e.remove all the plugs, boil and blow out the galleries, rings, replace cam and cam bearings, lifters, chain and sprockets, etc.

Elemental · 10-04-2007, 05:45 AM

X2. Why bother? If the engine runs fine, has in spec compression and oil pressure...Leave it.

If you HAVE to fix something, just wait.... Something will break.

gordo · 10-04-2007, 11:26 AM

Im getting ready to do this in my brother in laws truck. Its just a trail rig, gets very little use and we want to keep the costs down. It has very Low oil pressure and WORN out bearings. Seems pretty easy overall, except we are skipping the rear main/thrust bearing. Doesnt look like it would be easy to get out w/o taking the block out. The rods are really easy, the upper main bearings might take some finese though. If you replace the bearings with the same size you shouldnt need to mike to plasticguage anything right? Just clean the journals up a bit with some crocus cloth. I agree though if your oil pressure is fine and no knocking dont touch it. Ive got a 3.9 with nearly 300k and it runs strong! Gordo.

p76rangie · 10-04-2007, 02:35 PM

If the bearings are stuffed, you can bet that the rings are gone as well. I am not sure why you would put in bearings without doing rings as well.

TerryS · 10-05-2007, 03:23 AM

Quote:

Originally Posted by p76rangie

If the bearings are stuffed, you can bet that the rings are gone as well. I am not sure why you would put in bearings without doing rings as well.

X2, not to mention cam, cam bearings and lifters. LR cams are notorious for soft heat treatment, and go well before the rest of the bottom end. I have one (Don't ask me why I haven't pitched it) Well younger than 100K and several lobes are as much as .150" under.

roverandom · 10-05-2007, 11:28 PM

If your thinking that the engine is worn out and needs help it is better to rebuild the entire engine at once. It will save you money in the long run, last longer and give better performance. From your post it would seem that all is fine....for the moment. If I was you I would leave it be and save my pennys for a full engine overhaul when the time comes.