Steel rod life expectancy

[Ed Wright]

Every aluminum rod failure I had pulled into in the middle. Big eng spun freely on the crank, with a good bearing inside. All big end failures I have seen were bearing failures. If it's black, it sure wasn't the rod.
When you set your bearing clearances, think about the expansion rates.

[joespanova]

Originally Posted by Ed Wright

Every aluminum rod failure I had pulled into in the middle. Big eng spun freely on the crank, with a good bearing inside. All big end failures I have seen were bearing failures. If it's black, it sure wasn't the rod.
When you set your bearing clearances, think about the expansion rates.

This rod had a clean break right in the middle of the beam...........but the bearing was also blackened and destroyed........along with the rest of the big end in the pan..............the pin end was perfect

[Ed Wright]

That break was caused by the spun bearing.

[joespanova]

Originally Posted by Ed Wright

That break was caused by the spun bearing.

Well , in the end , I blame myself for be stupid enough to A) continue to run it when I KNEW the rods had been in there for a while and B ) being too lazy to tear it down over the winter where I may have seen a problem.....but , like I said I'm a slow learner

[Glenn Briglio]

Bearings don't usually fail by themselves. The connecting rod dimensions change or oil supply changes.

[Ed Wright]

Or clearances were wrong to begin with.

[joespanova]

Originally Posted by Ed Wright

Or clearances were wrong to begin with.

Not in this case. I'm a machinist for a major airline for 26 years.........and years prior to that. I have and have access to , every conceivable bore gauge and mic's anyone would need.
I assemble and check them........no chance in hell they were wrong.
Generally .0025-.003 at the vertical. Or whatever the rod manufacturer suggests.
I just ran it too long without an exam or freshening.

[joespanova]

Originally Posted by Glenn Briglio

The connecting rod dimensions change .

I suspect this was the case.............

[Dion Hildebrandt]

Originally Posted by Glenn Briglio

Bearings don't usually fail by themselves. The connecting rod dimensions change or oil supply changes.

Mine was instigated by detonation

[Ed Wright]

Originally Posted by Dion Hildebrandt

Mine was instigated by detonation

Yep. Hammering the bearings causes the ends to pull in & squeegee oil off the crank. Too much clearance often has the same effect, just takes longer.