Official S65 Rod Bearing Condition Example Thread

[Assimilator1]

Opps, forgot about this
I don't have any special camera, just my phone, but I took multiple shots before settling on a few. I checked them on my phone and they looked good at the time!
And yea I'll add the photos to his thread too.

Note to anyone whose jumped straight to this post, the wear down to the copper on this LCI shell did NOT occur in the engine, it's a result of me rubbing it with emery paper (across the shell). I just wanted to see what it looked like when the LCI bearings wear through the alu/tin babbitt layer.

As can be seen by the photos the copper is clearly visible. This is interesting as I thought I'd seen a few LCI shells that had worn through the babbitt giving a goldy-brass looking colour, but maybe that isn't the case. Perhaps their cameras have mis-coloured the copper? Or maybe it isn't the copper showing at all? [edit] Unless the babbitt layer is worn so thin it's translucent? (not the case for this one shell). In which case the colours of the 2 materials could be blending??

Has anyone ever seen an LCI shell removed which clearly shows copper like the photos below?

Thanks to helmsman for the donated shell from his engine (which had covered about 38k miles).




This one shows part of the shell's original wear patch in the middle, and the micro grooves left further up.
Direct link to Google photo which allows better zooming in.


Again showing part of the original wear patch (showing a goldy-brassy colour).


And you can see here where I've rubbed down on part of the wear patch it has returned to a silver colour.

[Helmsman]

Originally Posted by Assimilator1

Opps, forgot about this
I don't have any special camera, just my phone, but I took multiple shots before settling on a few. I checked them on my phone and they looked good at the time!

And yea I'll add the photos to his thread too.
Now can I direct link Google photos here?...... [edit], nope, I need to upload them to imgur I guess.

Note to anyone whose jumped straight to this post, the wear down to the copper on this LCI shell did NOT occur in the engine, it's a result of me rubbing it with emery paper (across the shell). I just wanted to see what it looked like when the LCI bearings wear through the alu/tin babbitt layer, as can be seen by the photos the copper is clearly visible.
This is interesting as I thought I'd seen a few LCI shells that had worn through the babbitt giving a goldy-brass looking colour, but maybe that isn't the case. Perhaps the cameras have mis-coloured the copper? Or maybe it isn't the copper showing at all?

Has anyone ever seen an LCI shell removed which clearly shows copper like the photos below?

Thanks to helmsman for the donated shell from his engine (which had covered about 38k miles).




This one shows part of the shell's original wear patch in the middle, and the micro grooves left further up.


Again showing part of the original wear patch (showing a goldy-brassy colour).


And you can see here where I've rubbed down on part of the wear patch it has returned to a silver colour.

Interesting! I haven't seen any 702/703 shells worn down to the copper, not according to the photos anyway. So maybe we all have replaced them just when worn in like designed by BMW...

[Adrian g.]

2013 DCT with 30k miles.

[IamFODI]

Originally Posted by Helmsman

Interesting! I haven't seen any 702/703 shells worn down to the copper, not according to the photos anyway. So maybe we all have replaced them just when worn in like designed by BMW...

Just the latest in a series of LONG-overdue updates to initially reasonable but thinly supported assumptions about these bearings.

We thought they were bimetal. Nope.

People keep saying rod bearings don't wear in. Glyco, who makes these bearings, explicitly says they can and do.

We assumed the discoloration patterns on these bearings necessarily means the top layer has worn through. Wrong again.

Looking forward to the next one!

[FMLYSDN]

Thought I'd just drop a preview of these. I will upload all the pictures when they're all out.

Background:
140,000km (87,000 miles)
3 Canadian Winters
Never revd over 3k until the car was warmed

And.....
57 Track days....

BTW....not my car but a personal friend.

[Assimilator1]

Look forwards to seeing all the bearings , those 2 appear good!
What year's the car and are they the original bearings?

Helmsman and....

Originally Posted by IamFODI

Just the latest in a series of LONG-overdue updates to initially reasonable but thinly supported assumptions about these bearings.

We thought they were bimetal. Nope.

People keep saying rod bearings don't wear in. Glyco, who makes these bearings, explicitly says they can and do.

Although I agree that their have been no photos posted here (or in my other 2 sources, or anywhere that I've seen) of LCI bearings that have worn through to copper (unless the colour of their photo is so bad it's hiding it?), according to everything I've read they still should not wear like they have, especially the low mileage ones.
Just as with Adrain g's bearings above, their is some wear on the shells which has (at least mostly) worn smooth the oil grooves 'built' into the shells, so these have been mostly wiped out and have removed a designed in feature. I doubt Glycol intended that.
I suspect the wear they refer to is from starting and stopping, and generally that doesn't show until a very long time, perhaps 100-150k+ miles? Where did you read where they discuss wear?

Btw, yea I need to revise my list, I will have to check each LCI entry (only) in the 'knackered' list. I suspect most LCI bearings should be put just in the 'excessively worn' list.

[FMLYSDN]

Originally Posted by Assimilator1

Look forwards to seeing all the bearings , those 2 appear good!
What year's the car and are they the original bearings?

Helmsman and....

Although I agree that their have been no photos posted here (or in my other 2 sources, or anywhere that I've seen) of LCI bearings that have worn through to copper (unless the colour of their photo is so bad it's hiding it?), according to everything I've read they still should not wear like they have, especially the low mileage ones.
Just as with Adrain g's bearings above, their is some wear on the shells which has (at least mostly) worn smooth the oil grooves 'built' into the shells, so these have been mostly wiped out and have removed a designed in feature. I doubt Glycol intended that.
I suspect the wear they refer to is from starting and stopping, and generally that doesn't show until a very long time, perhaps 100-150k+ miles? Where did you read where they discuss wear?

Btw, yea I need to revise my list, I will have to check each LCI entry (only) in the 'knackered' list. I suspect most, maybe all LCI bearings, should be put in the just 'excessively worn' list.

2011 and original rod bearings

[IamFODI]

Originally Posted by Assimilator1

Although I agree that their have been no photos posted here (or in my other 2 sources, or anywhere that I've seen) of LCI bearings that have worn through to copper (unless the colour of their photo is so bad it's hiding it?), according to everything I've read they still should not wear like they have, especially the low mileage ones.

Just as with Adrain g's bearings above, their is some wear on the shells which has (at least mostly) worn smooth the oil grooves 'built' into the shells, so these have been mostly wiped out and have removed a designed in feature. I doubt Glycol intended that.

Everything you've read where? Because most of the talk on this subject has been predicated on some combination of two assumptions:

1. That any visual sign of use on a rod bearing is bad, which literally zero rod bearing manufacturers agree with, and

2. That the discoloration on 702/703 bearings represents wear through the top layer, which you just disproved.

The grooves aren't "oil grooves" but channels for dirt particles to escape. Before we worry about them being partially worn away, we should find out how important it is for them to exist in their original width and depth all the way around the shell. Probably also worth finding out to what extent they're really worn away vs. filled in (and if the latter, then with what).

I've had some conversation with people at Glyco about this stuff. Showed them a few pics of 702/703 bearings in various conditions, which they said looked "probably... normal" for the miles. Let me see if I can get some more feedback from them that I can share here.

Originally Posted by Assimilator1

I suspect the wear they refer to is from starting and stopping, and generally that doesn't show until a very long time, perhaps 100-150k+ miles? Where did you read where they discuss wear?

It's in the Glyco PDF I posted here, which you also posted here.

Page 18 of the document, page 10 of the PDF:

If the clearance is minimal there is good conformability between the bearing and crank-shaft journal. This conformability is a result of material that is worn in some parts of the bearing in the order of magnitude of μms. This process leads to less local stress on the sliding layer, a better absorption of shock loads and less wear.

Running-in of bearings is mentioned on page 27 of the doc, page 14 of the PDF. They seem to suggest it happens very quickly -- in much less time than the hundreds of miles advised by shops -- but it's definitely a thing.

Originally Posted by Assimilator1

Btw, yea I need to revise my list, I will have to check each LCI entry (only) in the 'knackered' list. I suspect most, maybe all LCI bearings, should be put in the just 'excessively worn' list.

That'd be a step.

Without knowing what these bearings are made of, and with no reasonable way to estimate condemnation points, even just saying "excessively worn" is too confident. The only categories we can meaningfully assess at this point are:

1. Near-new
2. Somewhere between new and dead
3. Dead

[smokinjoe64]

`12 63K
Replacements - ACL/Carillo combo

What's the consensus on condition from expert eyes?

[Assimilator1]

Some wear, but not terrible.

No visible copper, right?

[akkando]

Saw this on Facebook. WCP coated bearings 40k miles. Brown spots are oil not cleaned off bearings.

[Assimilator1]

Appear to be in good condition, but yet again someone hasn't bothered to clean off the oil and it's hiding many of the shells in the exact spot we want to see, and they are low res pics .

[Assimilator1]

Originally Posted by IamFODI

Everything you've read where? Because most of the talk on this subject has been predicated on some combination of two assumptions:

1. That any visual sign of use on a rod bearing is bad, which literally zero rod bearing manufacturers agree with, and

2. That the discoloration on 702/703 bearings represents wear through the top layer, which you just disproved.

1. Where did you see that? Zero disagree AFAIR, with the exception of starting and stopping.
Which I haven't denied, but this only shows over very high mileages normally. The handful of bearings I posted links to which show virtually no wear, a couple of which had done over 100k miles support this, I appreciate that's not enough evidence though, and I'm trying to get more photos from local engine shops. (A mechanic friend of mine recently mentioned he pulled shells from a 160k mile Audi and they looked like new! Sadly he doesn't have photos or the old shells).
Oh btw, I also know their shouldn't be wear on them from past training, starting at college and after, the rare times I've stripped engines, and from other mechanics where we've talked about jobs they've done. Tbh, it's common knowledge, just not on here! Anyway, I plan to get photos to show this point, but it will probably take quite some time. Further complicated by coronavirus restrictions here in SE UK atm.

The grooves aren't "oil grooves" but channels for dirt particles to escape. Before we worry about them being partially worn away, we should find out how important it is for them to exist in their original width and depth all the way around the shell. Probably also worth finding out to what extent they're really worn away vs. filled in (and if the latter, then with what).

Yea true, my bad for picking the wrong description, I did as oil does flow through them of course .
The grooves aren't filled in btw, I used brake cleaner to clean that shell and it made zero difference to the wear patch. I'm not sure if the photos here are at the original resolution, but I know when I looked at them on my phone I could see their were worn down, the peaks of the grooves were wider for example.
It's true we don't know how important those 'flushing' grooves are, but they were designed in, and so those shells are compromised to some degree.

I've had some conversation with people at Glyco about this stuff. Showed them a few pics of 702/703 bearings in various conditions, which they said looked "probably... normal" for the miles. Let me see if I can get some more feedback from them that I can share here.

Would be good to hear, make sure you mention the mileage of the engine when you do.

It's in the Glyco PDF I posted here, which you also posted here.

Page 18 of the document, page 10 of the PDF:


Running-in of bearings is mentioned on page 27 of the doc, page 14 of the PDF. They seem to suggest it happens very quickly -- in much less time than the hundreds of miles advised by shops -- but it's definitely a thing.

That'd be a step.

Without knowing what these bearings are made of, and with no reasonable way to estimate condemnation points, even just saying "excessively worn" is too confident. The only categories we can meaningfully assess at this point are:

1. Near-new
2. Somewhere between new and dead
3. Dead

Btw, just to be clear, by excessively worn, I don't mean they are near death, just that they have more wear than they should.
And yea you could argue I could just lump the 'moderately worn' and 'excessively worn' into 1 group (I mentioned that in my earlier mega post), but I wanted to provide at least some graduation.

[Scharbag]

From Clevite - this is what bearings should look like. Also, most Cu/Pb S65 bearings seem to exhibit oil starvation wear as shown by Clevite.

[IamFODI]

Originally Posted by Assimilator1

1. Where did you see that?

Mahle/Clevite:


Rheinmetall Automotive:


And this, from Federal Mogul (same company as Glyco):


.


Takeaways:

1. Visually identifiable signs of use don't necessarily mean bad wear.
2. Rod bearings can and do break in.
3. Discoloration is not the same thing as wear that compromises functionality.
4. Different types of bearings will look different as they are used, so bearing wear patterns aren't comparable unless you know both bearings are made the same.

Originally Posted by Assimilator1

Which I haven't denied, but this only shows over very high mileages normally. The handful of bearings I posted links to which show virtually no wear, a couple of which had done over 100k miles support this, I appreciate that's not enough evidence though, and I'm trying to get more photos from local engine shops. (A mechanic friend of mine recently mentioned he pulled shells from a 160k mile Audi and they looked like new! Sadly he doesn't have photos or the old shells).
Oh btw, I also know their shouldn't be wear on them from past training, starting at college and after, the rare times I've stripped engines, and from other mechanics where we've talked about jobs they've done. Tbh, it's common knowledge, just not on here!

Still amazes me that we are comparing the S65 to normal engines...

What we need are other engines that are known to generate similar internal stresses, are used similarly, have the same kinds of rod bearings as the S65, and are built for the same or longer rebuild intervals. Such engines are rare as hen's teeth...

Originally Posted by Assimilator1

The grooves aren't filled in btw, I used brake cleaner to clean that shell and it made zero difference to the wear patch. I'm not sure if the photos here are at the original resolution, but I know when I looked at them on my phone I could see their were worn down, the peaks of the grooves were wider for example.

Worn down... but not gone, right?

Originally Posted by Assimilator1

Would be good to hear, make sure you mention the mileage of the engine when you do.

I did, hence the phrase "for the miles" in my post.

Originally Posted by Assimilator1

Btw, just to be clear, by excessively worn, I don't mean they are near death, just that they have more wear than they should.

No quarrel with your definition of excessive. That makes eminent sense.

The point is, we don't have a good idea about what "should" means.

Originally Posted by Assimilator1

And yea you could argue I could just lump the 'moderately worn' and 'excessively worn' into 1 group (I mentioned that in my earlier mega post), but I wanted to provide at least some graduation.

Of course you do. We all do.

We need a basis first.

[smokinjoe64]

Originally Posted by Assimilator1

Some wear, but not terrible.

No visible copper, right?

Fortunately, negative...

[Scharbag]

Originally Posted by IamFODI

Still amazes me that we are comparing the S65 to normal engines...

What makes the S65 so special? It is a 500CC per hole, multi-port injected, over square, high revving NA V8. Similar to Ferrari, Audi, Honda, Porsche, Lamborghini etc.

The S65 produces 104HP/L stock. Pretty cool. But other engines are similar.

The Honda K20A2 produced 100HP/L in 2001. 500CC per hole. 8250RPM limiter.

The Honda F20C produced 117HP/L in in 2000. 500CC per hole. 8900RPM limiter.

The Porsche 3.6L Flat 6 in the 996 GT3 produced 98L/HP in 1999. 600CC per hole. 7900RPM limiter.

Finally, the Audi 5.2L V10 produced 102HP/L. 520CC per hole. 8700RPM limiter in a V10!!!

My point is, the rotating assembly of the S65 (and S85) is not special. It is a wonderful engine, but there are a lot of wonderful engines out there that do not eat their rod bearings for lunch on a regular basis.

Cheers,

[Assimilator1]

IamFODI
The quotes are getting a bit big, lol .
Agreed with your 4 take away points.

Still amazes me that we are comparing the S65 to normal engines...

What we need are other engines that are known to generate similar internal stresses, are used similarly, have the same kinds of rod bearings as the S65, and are built for the same or longer rebuild intervals. Such engines are rare as hen's teeth...

Yes they are rare, I did try to find good pictures of good S2000 rod bearings but drew a blank, most of the few photos of S2000 bearings that are out their are of knackered bearings, from e.g oil pump failure. And the failures are very few and far between anyway. I did find a few engine shops with a page or video talking about an S2000 engine rebuild, but no photos or shots of the old bearings .
I haven't looked at the other cars that scharbag's listed yet, as those cars are much rarer, but I will look at some point.

Anyway, your point about finding comparable engines (like the ones scharbag listed) isn't really valid tbh, all hydrodynamic bearings in any engine (except maybe some race engines) regardless of revs or power are supposed to maintain the oil film during running and never allow metal to metal contact (assuming no contamination or engine faults).
So whether it's a tractor's 6ltr diesel turbo engine with say max revs of 3k RPM, a bog std hatchback with a 1.6 ltr max 6k RPM, a Honda S2000 2 ltr max 9k RPM, or the M3's 4ltr max 8.3k RPM none of them should allow metal to metal contact during running, and even by 100k miles (for the cars) should only show barely visible wear like the photo scharbag posted from Clevite's tech doc (my bad if I said no wear at all). Even at 100k miles, and tbh should easily last 200k miles if looked after properly.

But, I don't expect everyone to take my (our) word for it, hence I will be trying to collect photos of bearings from high mileage engines, high revvers would be nice, but realistically it'll have to be from any car petrol engine.

Missed or forgot the bit about 'for the miles' lol
Just rechecking the grooves in the photos now.....

[update] So here's a photo I didn't upload previously, I've linked directly to the Google photo as you can zoom in on that, (but you can't seem to from the imgur uploads , even after right clicking them, and selecting 'view page'). At the bottom part of the photo you can see part of the wear patch left which I haven't rubbed down, and you can indeed still see the grooves, although they are clearly worn to some degree.
And another Google direct link to one of the other photos I did post earlier.
Bear in mind this shell (and helmsman's other shells have only done 38k miles and are at the lighter end of the wear spectrum for S65 LCI bearings. I've seen much worse, I think some had good photos, I'll see if I can link them....
[update] This photo of LCI bearings by SYT_Shadow seem to show the grooves completely worn out?

Btw, this thread by deansbimmer shows some very high quality close ups of LCI and older bearings.
In the 7th photo down you will see the grooves have completely worn away except for the very edges, you will also see the goldy-brassy colour I have mentioned.
Seeing that photo again makes me think, although I (we?) haven't seen an LCI bearing clearly worn to the copper, I wonder if the goldy-brassy colour comes through as the result of the babbitt layer being worn microscopically thin, and maybe that distinct colour is a result of the babbit layer becoming translucent and hence blending colours? (sort of bourne out in the following 2 photos).
And this is obviously something I couldn't achieve by simply handing rubbing the shell with rough emery paper, I would need to use fine emery paper in a tool, and probably a polishing well too...... not sure I want to do that!

[atopa2002]

Originally Posted by Scharbag

What makes the S65 so special? It is a 500CC per hole, multi-port injected, over square, high revving NA V8. Similar to Ferrari, Audi, Honda, Porsche, Lamborghini etc.

The S65 produces 104HP/L stock. Pretty cool. But other engines are similar.

The Honda K20A2 produced 100HP/L in 2001. 500CC per hole. 8250RPM limiter.

The Honda F20C produced 117HP/L in in 2000. 500CC per hole. 8900RPM limiter.

The Porsche 3.6L Flat 6 in the 996 GT3 produced 98L/HP in 1999. 600CC per hole. 7900RPM limiter.

Finally, the Audi 5.2L V10 produced 102HP/L. 520CC per hole. 8700RPM limiter in a V10!!!

My point is, the rotating assembly of the S65 (and S85) is not special. It is a wonderful engine, but there are a lot of wonderful engines out there that do not eat their rod bearings for lunch on a regular basis.

Cheers,

https://f80.bimmerpost.com/forums/sh....php?t=1764410

Have you all seen this thread? The bearings doesn’t look much different with even less mileage .

[IamFODI]

Originally Posted by Assimilator1

Anyway, your point about finding comparable engines (like the ones scharbag listed) isn't really valid tbh, all hydrodynamic bearings in any engine (except maybe some race engines) regardless of revs or power are supposed to maintain the oil film during running and never allow metal to metal contact (assuming no contamination or engine faults).
So whether it's a tractor's 6ltr diesel turbo engine with say max revs of 3k RPM, a bog std hatchback with a 1.6 ltr max 6k RPM, a Honda S2000 2 ltr max 9k RPM, or the M3's 4ltr max 8.3k RPM none of them should allow metal to metal contact during running, and even by 100k miles (for the cars) should only show barely visible wear like the photo scharbag posted from Clevite's tech doc (my bad if I said no wear at all). Even at 100k miles, and tbh should easily last 200k miles if looked after properly.

"never allow metal-to-metal contact" = "no wear at all". If the second phrase doesn't apply, neither does the first.

"Assuming no contamination or engine faults" assumes parameters that simply don't exist in the real world. I see what you're getting at, but it's not relevant. Regardless of whether metal-on-metal contact (and thus wear) should happen in an ideal situation, the fact is that it does happen in real situations.

Good call mentioning service lives because it gets to what really counts here. It's not how pretty the bearing looks; what matters is how long it'll last, on average, before it fails in some way.

No hand-wringing about a bearing's appearance is meaningful until we know the relationship between its appearance and its longevity. We know that relationship pretty well for 088/089 bearings. We thought we knew it for 702/703 bearings, too, because we assumed the relationship was basically the same. Now that that assumption has proven false, we are back to the drawing board. For all we know, every 702/703 bearing in this thread had a reasonable chance of making it to 150k+ miles. That suggestion is no more or less premature than the suggestion that they're all excessively worn.

Originally Posted by Assimilator1

But, I don't expect everyone to take my (our) word for it, hence I will be trying to collect photos of bearings from high mileage engines, high revvers would be nice, but realistically it'll have to be from any car petrol engine.

It's not just about the redline. It's also about bearing stresses, which has to do with bearing size, crank and rod metallurgy, stiffnesses, vibrations, etc. etc. Not to mention bearing type.

Go ahead and grab your pics, but let's be real about what they'll actually do for us.

Originally Posted by Assimilator1

[update] This photo of LCI bearings by SYT_Shadow seem to show the grooves completely worn out?

Btw, this thread by deansbimmer shows some very high quality close ups of LCI and older bearings.
In the 7th photo down you will see the grooves have completely worn away except for the very edges, you will also see the goldy-brassy colour I have mentioned.

These pics don't have anywhere near the kind of resolution or contrast to make that kind of call either way.

Originally Posted by Assimilator1

Seeing that photo again makes me think, although I (we?) haven't seen an LCI bearing clearly worn to the copper, I wonder if the goldy-brassy colour comes through as the result of the babbitt layer being worn microscopically thin, and maybe that distinct colour is a result of the babbit layer becoming translucent and hence blending colours? (sort of bourne out in the following 2 photos).

Remember, when you sanded that bearing, it went silver before the copper showed. Wouldn't have happened if what you describe here were true.

I've read a mention or two of tin migration causing a darkening of the top layer. Could just be that.

[RedScytheM3]

Originally Posted by Assimilator1

IamFODI
The quotes are getting a bit big, lol .
Agreed with your 4 take away points.

Still amazes me that we are comparing the S65 to normal engines...

What we need are other engines that are known to generate similar internal stresses, are used similarly, have the same kinds of rod bearings as the S65, and are built for the same or longer rebuild intervals. Such engines are rare as hen's teeth...

Yes they are rare, I did try to find good pictures of good S2000 rod bearings but drew a blank, most of the few photos of S2000 bearings that are out their are of knackered bearings, from e.g oil pump failure. And the failures are very few and far between anyway. I did find a few engine shops with a page or video talking about an S2000 engine rebuild, but no photos or shots of the old bearings .
I haven't looked at the other cars that scharbag's listed yet, as those cars are much rarer, but I will look at some point.

Anyway, your point about finding comparable engines (like the ones scharbag listed) isn't really valid tbh, all hydrodynamic bearings in any engine (except maybe some race engines) regardless of revs or power are supposed to maintain the oil film during running and never allow metal to metal contact (assuming no contamination or engine faults).
So whether it's a tractor's 6ltr diesel turbo engine with say max revs of 3k RPM, a bog std hatchback with a 1.6 ltr max 6k RPM, a Honda S2000 2 ltr max 9k RPM, or the M3's 4ltr max 8.3k RPM none of them should allow metal to metal contact during running, and even by 100k miles (for the cars) should only show barely visible wear like the photo scharbag posted from Clevite's tech doc (my bad if I said no wear at all). Even at 100k miles, and tbh should easily last 200k miles if looked after properly.

But, I don't expect everyone to take my (our) word for it, hence I will be trying to collect photos of bearings from high mileage engines, high revvers would be nice, but realistically it'll have to be from any car petrol engine.

Missed or forgot the bit about 'for the miles' lol
Just rechecking the grooves in the photos now.....

[update] So here's a photo I didn't upload previously, I've linked directly to the Google photo as you can zoom in on that, (but you can't seem to from the imgur uploads , even after right clicking them, and selecting 'view page'). At the bottom part of the photo you can see part of the wear patch left which I haven't rubbed down, and you can indeed still see the grooves, although they are clearly worn to some degree.
And another Google direct link to one of the other photos I did post earlier.
Bear in mind this shell (and helmsman's other shells have only done 38k miles and are at the lighter end of the wear spectrum for S65 LCI bearings. I've seen much worse, I think some had good photos, I'll see if I can link them....
[update] This photo of LCI bearings by SYT_Shadow seem to show the grooves completely worn out?

Btw, this thread by deansbimmer shows some very high quality close ups of LCI and older bearings.
In the 7th photo down you will see the grooves have completely worn away except for the very edges, you will also see the goldy-brassy colour I have mentioned.
Seeing that photo again makes me think, although I (we?) haven't seen an LCI bearing clearly worn to the copper, I wonder if the goldy-brassy colour comes through as the result of the babbitt layer being worn microscopically thin, and maybe that distinct colour is a result of the babbit layer becoming translucent and hence blending colours? (sort of bourne out in the following 2 photos).
And this is obviously something I couldn't achieve by simply handing rubbing the shell with rough emery paper, I would need to use fine emery paper in a tool, and probably a polishing well too...... not sure I want to do that!

Originally Posted by IamFODI

"never allow metal-to-metal contact" = "no wear at all". If the second phrase doesn't apply, neither does the first.

"Assuming no contamination or engine faults" assumes parameters that simply don't exist in the real world. I see what you're getting at, but it's not relevant. Regardless of whether metal-on-metal contact (and thus wear) should happen in an ideal situation, the fact is that it does happen in real situations.

Good call mentioning service lives because it gets to what really counts here. It's not how pretty the bearing looks; what matters is how long it'll last, on average, before it fails in some way.

No hand-wringing about a bearing's appearance is meaningful until we know the relationship between its appearance and its longevity. We know that relationship pretty well for 088/089 bearings. We thought we knew it for 702/703 bearings, too, because we assumed the relationship was basically the same. Now that that assumption has proven false, we are back to the drawing board. For all we know, every 702/703 bearing in this thread had a reasonable chance of making it to 150k+ miles. That suggestion is no more or less premature than the suggestion that they're all excessively worn.

It's not just about the redline. It's also about bearing stresses, which has to do with bearing size, crank and rod metallurgy, stiffnesses, vibrations, etc. etc. Not to mention bearing type.

Go ahead and grab your pics, but let's be real about what they'll actually do for us.

These pics don't have anywhere near the kind of resolution or contrast to make that kind of call either way.

Remember, when you sanded that bearing, it went silver before the copper showed. Wouldn't have happened if what you describe here were true.

I've read a mention or two of tin migration causing a darkening of the top layer. Could just be that.

Are either of you qualified to debate the intricacies of bearing wear? We know this is a tired and contentious topic, which makes it a great platform for anyone off the internet to come throw around opinions and debate said opinions with very little references and zero citations of primary research literature. Unless you guys are qualified or experienced your debate is pointless. Just share information and leave your opinions out if you're not actively practicing in the field

[Scharbag]

Originally Posted by RedScytheM3

Are either of you qualified to debate the intricacies of bearing wear? We know this is a tired and contentious topic, which makes it a great platform for anyone off the internet to come throw around opinions and debate said opinions with very little references and zero citations of primary research literature. Unless you guys are qualified or experienced your debate is pointless. Just share information and leave your opinions out if you're not actively practicing in the field

Exactly.

And to all the Sn/Al engines owners who have spun rod bearings, the "theory" that 702/703 bearings are "better" is likely not very comforting.

Hopefully we get some more photos of proper clearance bearings in the next while as some engines have a good amount of use now.

Cheers,