What caused this rod bearing failure?

[squinn8810]

Hi!

I recently rebuilt and stroked my TJ's motor to a 4.6L. During break in, I would get a minute or two of what I initially thought was an exhaust leak but may have actually been detonation and/or something internal on the bottom end. Pulled the engine out and apart, rod bearing #3 was nearly welded to the crankshaft. Every other bearing looked perfect, main bearings good, cylinder walls good, camshaft and lifters looked surprisingly good as well.

My question is what would cause a single point of failure like this? Plugged oil galley? Bad clearances? I'm by no means an engine guy so crowdsourcing some opinions.

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[Cheromaniac]

Possibly either one or both of the two.

[Russ Pottenger]

Did you check your bearing clearances and if so what were they?

[dwg86]

Because of where the damage is i would think it was trash in the crankshaft oil hole to the rod bearing.it looks like, from what i can see in the pictures, that the damage is in line with the oil hole in the crank.

[dwg86]

What connecting rods did you use?

[2grimjim]

What Russ said; did you check ALL the bearing clearances when you assembled?

[squinn8810]

Because of where the damage is i would think it was trash in the crankshaft oil hole to the rod bearing.it looks like, from what i can see in the pictures, that the damage is in line with the oil hole in the crank.

This ended up being the root cause..found a price of debris in the block (no idea where from). Machine shop pretty much said the same thing you did that it was likely debris coming in from oil galley. Machine shop also said if it was bad bearing clearances I would've seen wear across the entire bearing.