Rcebowl

iTrader: (3)

sorry ... .hardcore noob question...

What extactly is a bearing??
What is the normal reason why is spinns?
just is your motor just died once it spinns??

Thanks,
Vincent

Greg K

iTrader: (2)

a plain bearing is a copper or copper/beryllium alloy that is used to separate steel parts in a high friction surface.

the main bearings are between the block and the crankshaft, and the rod bearings live between the crank and the rods.

bearings typically spin due to:
1) improper (cocked) installation - usually a very sudden failure within a few hundred miles
2) improper lubrication (oil starvation) - can take longer, but will fail suddenly.

spun bearings can be repaired sometimes, <edit: the spun bearing can't be repaired, but the block can sometimes be honed to allow installation of a new bearing if it was caught quickly enough> usually as part of an overhaul if the related damage to other components wasn't too bad.

EvoTio

iTrader: (10)

Very well said . Improper machine work also can cause a spun bearing, but that probably falls under the improper installation portion (not checking your clearances before assembly).

LIFER

iTrader: (16)

Spun bearings seem to be a common problem on the evo's... Most likely due to the ****ty oil pumps in them... If you spin a bearing, it is very expensive to repair, due to copper shaving in the oil, you have to replace the oil cooler, turbo, all bearings, all gaskets, have the head and block hot tanked, clean all the oil line's, and usually replace the oil pump and of course have a machine shop repair all damages.

Aby@MIL.SPEC

iTrader: (161)

I think the reason for so many evo's with spun rod bearings is due to whimpy rod bolts/big end flxing while being over revved. When the big-end is distorting, it can pinch the bearings onto the crank, whipping the oil film dry for a brief period of time, thus creating a metal to metal rotating surface. Once that happens, you start to wipe bearing material off the shell, then its all down-hill from there.

Other people may experience seveere detonation, which will just jack-hammer the heck out of the top bearing shell, resulting in the same scenario described above adue to oil starvation not neccesarilly due to th eoil pump & it's flow delivery capabilities.

just my opinion. I think that is why we see so many rod bearing failures & not main bearing failures.

another interesting tid-bit:

No one ever say's that the cam journals are also burnt up when they damage a rod bearing. The rear cam journals are the last place to get oil supplied by the oil pump, so this would make the rear cam journals the FIRST PLACE where you would oil starvation.