Thread: Oiling issue?
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      01-20-2012, 08:56 AM   #15
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Drives: 2010 M3 Coupe
Join Date: Jul 2006
Location: New York

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Originally Posted by BMRLVR View Post
Yes, if you have marginal clearance on any of the bearings and a problem don't manifest itself before 20k miles or before, there is a good chance you won't have an issue with that bearing.

In 1997 my brother and I installed 2.9 liter OEM euro pistons in a VR6 engine from his Corrado. With the Euro pistons you reuse the stock rods and replace the wrist pins and bearings. When we took the engine apart all the bearings looked good for the mileage 70,000 Miles.

Once the engine came back from the machine shop we began to reassemble it. We checked all the rods and mains with plastigauge and all were nice and even and in spec.

After only 1,000 Miles of use the car started making a loud clicking noise that was quickly getting louder. We got the car home pulled the oil pan and soon saw the rod bearing on #1 cylinder had started to lap the bearing (all the other bearings were good). Luckily enough, the crank journal was only lightly marred so we replaced that bearing, again checking for clearance and it seemed ok. In even less mileage than the first time, the bearing failed again.

The cause of this was that the rod was slightly stretched. Since all the bearing that we took out of the engine looked good we didn't spend much time measuring the rods since all of the OEM bearings looked good. We ended up changing all six of the rods and the engine worked beautiful and is still running to this day (in the possession of a new owner who is a friend of my brothers)!

The point I am trying to make is that in many cases, bearings will conform to a shape and then will last just fine. I am quite sure by looking at the bearings that we took out of that engine, it would have went for another 100000 miles easy. If it weren't for us putting new bearings in the bottom end we never would have known the rod had a stretch issue at all.

BTW, when you changed the bearings, did you re-use or change the rod bolts?
Used rod bolts can have an effect on center-to-center length, no?
Did you do anything for the marred journal? Probably nothing a little emory cloth and a string couldn't fix?
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