Steel rod life expectancy

[Dion Hildebrandt]

Originally Posted by joespanova

In a situation like mine , where you lose an aluminum rod..........was it a bearing / oiling failure that caused the rod to fail...........or the rod getting kicked out of shape that made it "appear" to be a bearing failure? Hard to say.........the crank has bearing metal transfer that was obviously hot...........but why? Which came first ? Is the oil system adequate ?
Rods probably have 120ish runs on them.

Cut open the oil filter, it will give a better picture on what happened first. Had the same thing happen recently, and the filter was loaded with brass indicating a bearing failure.

[joespanova]

Originally Posted by Dion Hildebrandt

Cut open the oil filter, it will give a better picture on what happened first. Had the same thing happen recently, and the filter was loaded with brass indicating a bearing failure.

Good point. In aluminum rod combos where the rod has plenty of cycles you would tend to think its a rod failure , BUT , a bearing failure is certainly a possibility......... with the rod getting kicked / stretched out of shape that in itself may have caused the bearing failure.......chicken or egg?

[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.