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Strange main bearing wear

COCHEV

COCHEV

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Anyone see this type of wear?

Early 70s 350 mystery engine that was "rebuilt". #1 main.

Bearings are clevite p series

uploadfromtaptalk1381239645724.jpg

uploadfromtaptalk1381239665282.jpg
 
It is worn in a weird spot,usually they wear at the top and bottom away from the rod halves..looks like a peice of it got torn out by something?..

I know many chevy V8 engines with A/C have the #1 bearing wear more than the rest due to the load from the A/C compressor,plus the fact its the furthest one away from the oil pump and gets less oil pressure..
 
Completely un-educated guess, but the cap bearing surface isn't uniformally flat, and the bearing isn't sitting flat right there?

Could be a reflection, but it appears that there might be a little burr right there on the edge of the cap, where the bearing is washed out? Sure looks to me like it's wear more than something gouging it.
 
No, there looks to be a tiny little shiny spot just above the wear spot on the bearing, on the chamfered edge of the cap. Like what I'd expect if it had been hit with something that had an edge on it.
 
Thanks for all the replies. This is the only odd bearing. It did, however, spec out just fine with plastigage. As did all the other mains and rod bearings.

Might just button the pig up with some new gaskets and run it....
 
dyeager535 said:
No, there looks to be a tiny little shiny spot just above the wear spot on the bearing, on the chamfered edge of the cap. Like what I'd expect if it had been hit with something that had an edge on it.
Click to expand...

See it now. It's about 2 pixels worth on my laptop. Your eyes are way better or your screen is.
 
Maybe its something funny with the pic. I don't remember any other damage spots
 
What if you lay a straightedge along the cap from front to rear in the general area of that wear spot?

It seems so localized to me that it wouldn't be a reciprocating part issue. If it was the crank, it would have wiped the bearing all the way around. Looks like a high spot that is worn down to me.

If oil starvation, what would cause it just in that area? Honest question, not arguing, just can't envision how that would cause a localized issue right in that spot.

Plastigauge spec'd out the same in that exact spot of the cap on the opposite side, with a good bearing? Or do you just mean the plastigauge installed in a random spot spec'd out ok?
 
Plasigage was done right on top so to speak of all the bearings, if that makes sense. Guess I could check it right on the wear spot and see what I see....
 
I would, just to see.

I certainly don't tear down enough motors to know all the various failure modes of bearings, but it just seems reasonable to me, either oil starvation or a high spot on the cap.
 
COCHEV said:
Thanks for all the replies. This is the only odd bearing. It did, however, spec out just fine with plastigage. As did all the other mains and rod bearings.

Might just button the pig up with some new gaskets and run it....
Click to expand...

you should not only use plastigauge, but use a micrometer to measure the main journals in 3 positions left to right, and in each of those positions measure it every 120 degrees. this will tell you if you have taper or out of round journals. plastigauge will not, thats just oil clearance.
 
wage92 said:
you should not only use plastigauge, but use a micrometer to measure the main journals in 3 positions left to right, and in each of those positions measure it every 120 degrees. this will tell you if you have taper or out of round journals. plastigauge will not, thats just oil clearance.
Click to expand...

Yeah, I know, this was just going to be a quick n dirty swap for the burb cause I'm loosing the head gasket on it. Then I can build the original motor...

At least that's the current thought. But that changes...with the wind
 
seems to me, like if only the bearings are changed, the same thing will most likely happen...how long it takes to happen, who knows :dunno:
 
So I plastigaged it right at the wear spot. It did show a slight uneven wear (skinny to fat) however still all within spec :dunno:

Buttoned up the bottom end today. Going to run it as is. Shouldn't be into it more than $500 not counting doing the clutch while its out.

Oh and the one piece pan gaskets are the cats pajamas:thumb:

Now if I can just find the motivation to pull and restab an engine with a sm465. Ugh. Might pull the core support and pull em out together and reinstall the same way...
 
y5mgisi said:
Oh dont be a baby. Just un bolt it from the bellhousing.
Click to expand...

Its not the unbolting I'm dreading. I hate stabbing the damn thing back in....

There will be plenty of beer provided if you want to come join the party...
 
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