my DIY engine rebuild

[hemonu]

I had that twice in my life, but on a motorcycle engine quite a while ago. A few thouhgts.

Root cause is usually a lack of oilf pressure / flow in the bearing. If the engine is very old and worn the gap may be too high to maintain enough pressure. If the engine is not worn, there may be a problem with the oil pump or an oil line is clocked. Both happened to me. I think it should be possible to grind and polish the crank to the next smaller bearing diameter as it looks. But you have to measure first.
If the bearing has really turned inside the piston rod, you have to change the rod. But I'm surprised that the clips at the corner of the bearings are not broken. When it happened to me the engine got totally overheated in a minute and the bearing was complety destroyed.

[flaps10]

Originally Posted by hemonu

snip
But I'm surprised that the clips at the corner of the bearings are not broken. When it happened to me the engine got totally overheated in a minute and the bearing was completely destroyed.

You know, I had put my tools away and gone about my life for a couple of hours when I had the exact same thought. So I went back out and took a careful look.



As you can see, both tabs are knocked off. I'm pointing at one of them still where it is supposed to live. The other one presented itself when I first removed the rod and bearing. It was just sitting on the crank and at the time I didn't know where it came from.

It would appear rods come in sets of six, and they're about $1500. I'd like to think I could get a single rod and have them all balanced as a set.

That I can tell, there are no scratches on the crank that would justify turning it to the next size down (which btw, aren't commonly available for the M96 from my first glance), but would respond well to a polish job.

I'm making a call to a local hot rod shop that has the capacity to do ultrasonic cleaning and do the polish work.

[hemonu]

Originally Posted by flaps10

I'm making a call to a local hot rod shop that has the capacity to do ultrasonic cleaning and do the polish work.

If it is a good shop you can trust, they may be able to polish and balance a set of piston rods at a reasonable price. That might allow to integrate a used one and strength and balance of the engine would be even better than OEM. For the damaged piston they also should be able to measure the wear of pistons and bore and than you can decide to change one or all. But after 120k and engine opened ...

I remember changing a single broken piston ring on the engine of my first car. I was young, still at school and had little money Only a few weeks later the next was broken ;-)