I picked up this motor cheap. The rod bearings are ugly. Incorrect bearing or no oil changes? Engine is cleannn clean inside

 

Looks like debris in the oil to me, and a couple big pieces. Wiping off the bearing might be more helpful to look at.

 

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Interesting that the rod bearings would be messed up but not the mains, or did you just not get to the mains yet?

I'd be more worried about where the debris came from. Looks like little specks of metal embedded in the bearing. And it looks like wear from lack of oil as well. Based on my past experiences, I'd make a beeline to the rearmost intake cam journal and start examining the bearing surfaces in the head. Damage accumulates there quickly if you have oiling and debris issues. If the cam journals are fine, maybe it was just a brief one time event that scuffed up the bearing and nothing to worry about.

My feeling on rod/main bearings is that they're pretty tolerant of wear to a certain point. I'm intentionally running clearances outside the factory spec (still well under the maximum clearance tho) and I get great oil pressure and no problems. Having a little scuffing on the bearing is more of a bad sign than a bad thing in itself. I'd still replace the bearings because you're in there already. How does the crank look?

 

Looks like infrequent oil changes or low oil, I'd check #4 bearing for the most possible damage/heat spots. Does look like small flakes pressed into the bearing.

I'd replace wear items when rebuilding. How do the cylinder walls look?

 

well i tore the rest down

cylinder walls are nice and smooth simple hone and rering would work there

the mains look pretty nice, within factory spec

the rods though, are another story. it seems like whoever assembled it, either didnt measure the rod bearing or purposely used a too tight bearing? with the wear, im measuring about .014-.015 clearance. factory manual calls for .018 to .029 seems the crank was clearancing out the bearing. the crank surface looks OK, but ill give it a light polish before reassembly to get any deposits off. i could not find any brand or numbers on the bearing, so im assuming they are some cheapo ebay brand, prob all aluminum and not good for much other than a paperweight.

 

Think you're missing a zero in your measurements..... .015" would knock .0015 would be tight but not too crazy.

 

I was thinking the same thing....

 

.0015 is .0001 over the upper limit of the standard spec (though well under the maximum of .004). What do you mean by tight? (I only know this of the top of my head because I did my rebuild recently and I was at .0015 for the mains)

 

Just that, it's on the tight end of the tolerance. It's fine, there are some engine builders think there is increased chance if wiping a bearing with that little of an oil film which is why you see loser bearings in a race motor. I wouldn't change it or freak out.

 

If I had to guess, the thing was dirty when it was put together, or there was crud in the crank oil passages. Maybe they cut the crank and didn't clean the oil passages in it after?

Also, they look worn a touch unevenly. Is it possible the rods are out of spec. My rods were tapered in bore, and I had to have them line honed. This wrecked a set of rod bearings for me (I never ran the engine, just stupidly turned it over with them in it).