Is this main bearing cap normal?

[jaredmac11]

Im looking at the main bearing caps and bearings and one bearing and cap in particular stands out.

At first I thought a bearing spun and worked down the cap and crank. But then I noticed the bearing is completely different from the rest.

http://imgur.com/a/jBSpY

Can someone let me know what's going on? The bearing set I purchased online does not have this particular bearing in the set with the additional grooves. It completely stands out.

The final image shows all the caps lined up, the penultimate cap has a pattern worn in. Either from a slipped bearing or from the factory.

Every wall of the crank has a bit of a lip, but the wall for that bearing is flush.

[roguetoaster]

I don't know for certain, but that looks an awful lot like an M50 cap, seems like ones I've seen in the yard have that groove. But it may just be one cap that's machined that way for some reason.

[jaredmac11]

I don't know for certain, but that looks an awful lot like an M50 cap, seems like ones I've seen in the yard have that groove. But it may just be one cap that's machined that way for some reason.

numbers match all the other caps.. but the m50 bearings fit the M42 so for all we know they are all the same. I see the engines commonly referenced together; m50, m42, s52 with workshop manuals so they could all be the same.

[TobyB]

Where's your thrust bearing?
Is it now paper thin?
The one that looks different also looks to be machined for a bearing with thrust surfaces....

As to swapping caps, it usually doesn't work- the block and caps are final- bored
together, so each cap is somewhat unique...

t

[jaredmac11]

Where's your thrust bearing?
Is it now paper thin?
The one that looks different also looks to be machined for a bearing with thrust surfaces....

As to swapping caps, it usually doesn't work- the block and caps are final- bored
together, so each cap is somewhat unique...

t

Holy crap. I couldnt even find the main thrust bearing, but that cap is the 4th cap, aligning with the main thrust bearing on the realoem diagram. Either it was machined to fit a non thrust cap, or the sides of the thrust bearing completely worn and those markings are from the cap rubbing against the crank. Is that plausible?

there were no shavings in the oil when I changed it so this was likely fixed.

[TobyB]

It's possible it's worn that bad. The M42 only got a half- shell,
and is pretty notorious for having thrust issues... in more than one way...

And yeah, there's a fix involving... M52 bearings, maybe? I forget... might explain
the oddball cap, if the original got munched.

t

[jaredmac11]

edit: Actually, the main thrust bearing wouldnt go on the cap, so I was mistaken. I just got back to the garage for another look and the main thrust bearing is where it should be on the block. What throws me off is the crankshaft, block and cap. Block and cap both have that worn semi circle along the wall of the cap and block. The crank is missing that lip. Im wondering if this is all factory or not.


Could anyone verify?

[Fsnow]

Is it possible that the thrust bearing had worn so much that your cap and block had become the new thrust surface?
How much crank endplay do you have?

[jaredmac11]

Is it possible that the thrust bearing had worn so much that your cap and block had become the new thrust surface?
How much crank endplay do you have?

It's hard to say. I do know there are no shavings in the oil. It was just dark and due for a change (I never saw it run). The main thrust bearing is there, I was mistaken before. I thought it was on the cap but its at the bottom, on the block.

As for end play, when I grabbed the crank pulley, there was some movement back and forth, but not a lot. I didnt know how to measure it, but certainly not a lot. I could just hear clacking from the crankshaft bumping the block.