1Revvin7

The question still remains, at what point should you replace your bearings? How much copper is too much?

GMON

At $10 a bearing I would think any coper is too much. But I am on my first rotary rebuild. What ever happend to plastigate



Gregory

mazdaspeed7

Did you fail to read those excellent posts by Lynn, or was it just past your comprehension?

BDC

That was a little rude. Perhaps you could answer his question, then.



B

kahren

pistons and connecting rod bearings dotn get along for some reason, i havent had a bearign problem yet with a rotary

1Revvin7

"So there is that aspect. If I have a bearing in a stationary gear that has been to 9,800 many times, with no problem, would I change the bearing just because the engine is in pieces? No way in hell will I do that. The bird in the hand solution.



You cannot just go on forever doing that, but it is a great general rule. Too much bearing clearance, makes for low oil pressure at low RPMs but for a nice fat oil film at speed"



So please tell me how that is clear?

No one asked for a general idea of yea its ok, but AT what point is too much too much? Take a chill pill man.



But once again if the motor is out WHY NOT replace them? Is increased break-in time the only downside?

GMON

I read the post, comprehended it, and greatly thank Lynn for it. However, the question of "when" to replace has not been clearly answered.



Gregory

mazdaspeed7

Little harsh? Sure. Out of place? Not to me.



I guess thinking for yourself is just a little too hard sometimes. From Lynns post, and common sense, its reasonable to assume that bearings should be replaced when the clearance is large enough to adversely affect the oil pressure. Thats the *need to be replaced* level. Anywhere between there and new is very subjective, and is totally up to the engine builder whether the bearings would be better off being replaced. One exception though would be abnormal wear. If there is abnormal, or excessive wear, it should be replaced. Anything else its more a matter of personal preference on how you want the clearances set in your engine. Thats a whole different subject though.



Lynn, how about a thread with your thoughts on engine clearancing? I would love to read that, as Im sure many people here would.

Lynn E. Hanover

All copper is not too much. Machining away all of the overlay is a method of increasing oil film depth and adding a pit of room for the sine wave shape of the crank. So when you scream the engine, and the crank bends a bit you don't skin up the ends of the main bearings.



It would take so long, and so many starts to were away a large amount of overly in normal operation, that large unclad areas would indicate replacement just for

fatigue breakdown would be in order. If you see small cracks forming in the overlay so it looks like the drying mud in a puddle indicates long term stress breakdown. But that takes a long period of abuse.



So if overly is missing from street run bearings, it is usually time based, since the wear comes from cold startup with no oil pressure, and to a lesser extent acid attack from never changing the oil. Copper showing in that case would require new bearings. If overlay is missing from any location on a street bearing, other than across the puzzle lock, pitch the bearing.



Lynn E. Hanover

1Revvin7

Ok now that makes sense. Now I just need that tool to measure the bearing diameter...