Causes of main bearing failure

[indianajoel]

The main bearings went bad in one of my LA318's. I hear contradictory info from people on this: can bad timing (too advanced) damage the bearings?
Some people say yes and some say no, so I thought I'd survey your guys' opinions.

FWIW, mine were all worn down to copper, the crank journals are scored, one saddle in the block cracked, and before I pulled it, the engine had good oil pressure at start up, and running down the road, but real low pressure at idle after it warmed up. I assume that's because the bearings were bad and not the cause of them going bad.

thanks for help.
-Joel

[EGroscup]

Which came first, the chicken or the egg? My guess would be that the cracked saddle started the whole mess, the oil pressure drops as the clearances open up then they start wearing. More wear less pressure and into the death spiral we go. My theory at least. Erik

[elacruze]

The cracked saddle as well as the rod bearing failure can also be a result of a long-term detonation problem.

[chilort]

The cracked saddle as well as the rod bearing failure can also be a result of a long-term detonation problem.

What he said.

[truckluvr]

which saddle? #2? Long term detonation will cause (usually) rod bearing failure before main bearing failure. A cracked saddle can be caused by many things. Casting flaw from the factory, excess heat due to overheating/lack of lubrication, overrevving, out of balance issue... If you want to play sherlock holmes you could check pickup tube for clog, dampener for slippage, lifter galleys for blockage etc.