Hi all,
I have this 86.5 engine that has sat quite some time. This is the one that the previous owner’s wife broke windows out of and dented the fenders. There was also a couple of cubes of glass evident in the crankcase as this all happened when the intake was off of the car.
Anyway, I knew I needed to break it down to a degree to ensure no glass was there.

I have the heads off and will be taking them to a shop to get worked over.

For the block, I am curious on whether to do the bearings/rings while I’m here

I have the rod bearings off already and have read about the thrust bearing issues (this is an automatic) so I want to do whatever I need to keep that from happening

Here’s what I found:







Are these original rod bearings?
I see lots of rod bearing options out there but not a ton of mains for sale
thanks all!

 

My ‘85 with 71k (indicated) is the mother of all WYAIT projects. I kept taking it apart further and further.

And it paid off, for me. The only thing actually wrong with the engine was a #1 main bearing that was showing copper. Speculation on cause has been either worn harmonic balancer or the tension from an accessory belt.

People said for a very long time that the main bearings on 928s are always fine, but in my sample size of 1, that wasn’t the case.

I ended up just getting a set of mains from Porsche. Still sitting in a box like the rest of the car.

 

Thanks,
I should mention mine shows 138k miles - so may be ready regardless

 

Someone was there, before you.
Those are Glyco rod bearings, not Factory Porsche rod bearings.

Main bearing set comes from Porsche....
Or you can buy a set of Glyco 944 main bearings (recently available again), throw the center thrust bearings in the trash, and buy the correct center thrust bearings, from Porsche. (This will save you a few hundred $$$$.)

 

Were any accessories removed?

 

Nope. Air pump belt was still intact. What’s the 2:00 belt, power steering pump? That’s where the damage was localized. I




Sorry to get off topic, grillage. But if you’re comfortable with re-sealing the block halves, and the engine is already out, I still say take a look. Then you know you’ll be good for another 40 years.

 

My 85' Auto S2 with at least 88k miles looked like that. Rod bearings were a bit worn, all other mains good apart from that on one the crank nose - I suspect this is caused by a tired damper. Resealing the block is not so bad.

 

Thanks guys. I have re-sealed blocks before. I even learned what not to do on my old Maserati Biturbo when I overapplied and blocked some oil passages.

I’ll crack it open and see what everything looks like

 

I would tend to agree, but I thought a shot damper was more chatty around the entire shell, not just one place.

 

This is typical alternator belt load wear, occurring at cold starts.
Every single '85 and later engine looks like this, or worse.
Damper deterioration shows up in different places.

BTW: The vast amount of alternator belt wear and the need for the crazy tension occurs at engine shutdown. My updated Bosch high output alternator has a freewheeling pulley, which eliminates this belt wear and reduces the need for excessive tension.

 

Glad I dug into this:
Here’s what I found:

All oil rings stuck. The car had REALLY thick oil in it. To the point of when I pulled the plug out nothing came out for 30 seconds.





small crack and worn front bearing:



The rest show wear enough to replace:

 

Good catch.
Re front bearing there is a join with a key feature that looks like a crack but is normal. Note its tricky locating the bearing when you reassemble as you need to locate the roll pin in the hole that is presumably there to stop bearing movement/rotation.

Note also in case you are thinking about getting the crank journals polished, there has been much discussion about sludge entering the oil galleries and being difficult/impossible to remove completely. There has been previous discussion about this contributing to engine failure. When i redid my bottom end I had the journals polished before i realised this but if i were doing it again i think i would leave them as is unless there was major damage. Greg et al can say more about this - i only have a data point of 1 and still havent restarted my engine to know if i did a good job!

 

When I did mine I got rod bearings and rings from Roger, but Sunset had the best price on the mains. There seems to be confusion as the whether the current part number for the thrust bearing contains two parts (upper and lower) or only one. So much so that, when I got my complete main bearing set from Porsche, I ended up with four parts (two complete thrust bearings). I have no idea what was supposed to be in the boxes, but I got two boxes and they both contained two bearings. I'm ok either way as I have another engine to do soon, but still. I generally try to avoid the while-we're-in-there syndrome, buy right now I would say that most 928 motors need head gaskets, and you better at least check rings and bearings at the same time. Like you I found, not so much wear on the rings, as a lot of build up.
If you are sending your heads to the shop, make sure you mark them in a way that will not come off with the cleaning or take note of the size numbers so you know which is which. They are ALMOST swappable, but not quite.

 

Same thing happened to me with Delaware Porsche. Offered to return them and they insisted they sent what I ordered. Now I have a set of thrust bearing for free.

 

Yup, been that way for about a year or so.
In that time I've bought 14 sets of main bearings....and thus have 14 "extra" sets of thrust bearings.
Combine these with a set of Glyco 944 main bearings (throw away the set of thrust bearings in the 944 set) and I've got a pretty sweet price on 14 complete sets of late model 928 main bearings.