Thread: Strange wear pattern on big-end shell bearings

I don't think I have ever seen anything like that either. I wonder if it is an artifact from running with very dirty oil or perhaps low oil pressure, so that the pressure is not spreading the oil right across the journal?

What type of oil has it been running? Conventional non-synthetic?

Originally Posted by Slunnie

What type of oil has it been running? Conventional non-synthetic?

In the short amount of time I've had it running ......conventional 20W50 prior to that who knows ?

I did wonder if there are two raised sections on the steel backing, when you wear through the white metal they come into play ??

Being a hydrodynamic bearing the shells only come into contact with the journal briefly on startup or if there is a loss of oil pressure. Going through to the backing would, long term, wear grooves in the journal.
When the new bearings arrive I'll remove the other three and see if they are the same.


Colin

Wow. That's weird. If there were any decent engine builders left I'd ask one of them. I would have thought if it was a low pressure thing then the oil wedge would fail to form across the whole bearing face. Impurities seems more likely to me, but I don't claim expert status.

As for the Army replacing the crank, that would really only have been done at a Base Workshop, probably not at a detached or field shop. I'm tipping you don't have any records of this. There would have been a paper trail, because the Army had whole battalions of clerks back then, unless the car was in theatre when it would be anyone's guess, but major work like that would be unlikely. Anyway, I digress. The Army certainly did major overhaul work, at least at 2 Base where I was for a time. A new crank, in heavy greased paper, could have been sitting on a shelf in Stores for years. They did things like that back then.

Just a moment...

Matches your pattern. Given low oil pressure maybe you were on the verge of more significant damage?

Could just be the optics in the photo, but are the right hand edges of top and bottom shells not entirely square?

And another possibility - imperfect journal geometry https://www.kingbearings.com/wp-cont...cape-Guide.pdf

Originally Posted by workingonit

Just a moment...

Matches your pattern. Given low oil pressure maybe you were on the verge of more significant damage? The tangs would stop the shell spinning and weren't damaged. Oil pressure was low but not that low.

Could just be the optics in the photo, but are the right hand edges of top and bottom shells not entirely square? They are square, it's the angle of the photo.

And another possibility - imperfect journal geometry https://www.kingbearings.com/wp-cont...cape-Guide.pdf Maybe, great fault finding chart though.

The motor has been running with those bearings for a fair amount of time. Possibly while still in service then the previous owner and then to me. I've been slowly bringing it back to roadworthy condition and have only started & run the engine 2-3 times per year moving it around the property. Mind you I've owned it for a few years.....
2a GS Refurb ARN 178-334

Replacement shell bearings have left the UK, it'll be interesting if the other shells show the same wear pattern when I drop the big-end caps.

Colin

Well that'll teach me to look in an old Series II manual, the shells turned up and they are not the correct ones !

Turns out the engine is an early Series II 2.25 and the big end bearings are a different size to the later II, IIa & III motor.
Part number on the original shells is 248747 (probably a supplier number rather than a LR number) in a workshop manual I found pn 239834 which seem to be obsolete or advertised at a crazy price.

I may have to re-assemble with the old shells to keep the vehicle mobile while I either track some down or consider an engine swap.

Colin

Originally Posted by gromit

...track some down or consider an engine swap.

I believe Len Beadell would just make new ones from a saucepan.

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