Steel rod life expectancy

[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.

[Ed Wright]

Originally Posted by joespanova

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.

SBC? Why so much clearance? You do know that aluminium rod will expand much faster than the steel crank, right? Imagine how loose they are at operating temps. I don't run my steel rods that loose.

[joespanova]

Originally Posted by Ed Wright

SBC? Why so much clearance? You do know that aluminium rod will expand much faster than the steel crank, right? Imagine how loose they are at operating temps. I don't run my steel rods that loose.

Well , I don't know what to tell ya........engine builders a lot smarter than me have run em that way for years........if I ran em tighter and it failed I'd be blaming it on that.........

[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.