If bearing clearances are small enough, it's possible for the bearing to shift in the mount, a so-called spun bearing, misaligning the oil feed holes and starving the bearing for oil. The bearing heats up and wipes out the bearing material. Soon the bearing backing which is steel rides directly on the crank shaft. If lucky you can catch this process before the crakshaft is damaged and just put in a new bearing.
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05:09 PM
Formula88 Member
Posts: 53788 From: Raleigh NC Registered: Jan 2001
Like he said, the bearing actually "spins" in the bearing race. That's bad. Then you get no oil control - no oil flow where it needs to be, and it causes you to loose oil pressure as well. Typically you going to have to at least hone the bad journal, or have it turned. You can get oversized bearings to take up the slack after you turn the journal or rod end, if it's not too bad. Otherwise, it's time for a new crank and rods.
Spinning a bearing is real bad. Worse is breaking a piston, piston pin, piston ring, etc., because then you have parts fragments flying around inside the block and that can royally screw things up - even punch a hole in the side of the block in extreme cases!
BTW, that's why Fiero's would catch fire. The connecting rods were crap, they'd fail and break through the side of the block - pouring hot engine oil onto a very hot catalytic converter - POOF!
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05:27 PM
Elvira Member
Posts: 933 From: Frankfort, Kentucky Registered: Jun 2001
Originally posted by avengador1: Ask Elvira, she has recent experience in this, or try to find her post about it.
Well, I bought my blue GT with a spun bearing. It knocked really bad. We bought a "professionally built" Fiero V6 off of EBay. I put 1000 miles on the motor and it lost oil pressure. We changed the oil pump and it got even worse. We had our mechanic pull the main bearings and they were so grooved and pitted, I am surprized it didn't knock! I am bringing the bearings to Kick Hill tomorrow to show them to Eric, if anyone else wants to see them, they can. That is a spun bearing, I believe. When the crank/bearings get grooved, it causes a knock and all the other problems that come with it. You can get the crankshaft turned like .10 under, 20 under, etc. and get the bearings that coincide if it isn't that bad (mine's totally wasted) and basically rebuild the bottom end. I am just going to get Chester's freshly built 2.8 and he is going to a V8. I learned a valuable $2500 lesson, NEVER take a stranger's word on something that you can't visually inspect. See everyone at the NEFA Swap Meet tomorrow! We will be the one's in the Intrepid rebody!
------------------ Elvira President, New England Fiero Association (NEFA) Blue 87GT 5sp Black 86GT 5sp 86SC t-top 58k miles 84 Indy 87 4-seater (2+2)
Caution should be used whenever you have a bad rod bearing, because in most cases it's the rod cap that failed (elongated-stretched) that caused the bearing to fail. Of course very high mileage engines would be an exception. Rods should always be checked, otherwise you might end up doing the same job again a few miles down the road.
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09:09 PM
Apr 21st, 2002
Elvira Member
Posts: 933 From: Frankfort, Kentucky Registered: Jun 2001
Originally posted by California Kid: Caution should be used whenever you have a bad rod bearing, because in most cases it's the rod cap that failed (elongated-stretched) that caused the bearing to fail. Of course very high mileage engines would be an exception. Rods should always be checked, otherwise you might end up doing the same job again a few miles down the road.
Definitely true! If you are going to do the mains, makes sure you do the rod bears also. It will save you $$ in the long run. The bearings are pretty cheap also. Don't forget an oil pan gasket. Good luck!
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07:57 AM
GTDude Member
Posts: 9056 From: Keysville, Virginia, USA Registered: Nov 2001
I am bringing the bearings to Kick Hill tomorrow to show them to Eric, if anyone else wants to see them, they can. That is a spun bearing, I believe. When the crank/bearings get grooved, it causes a knock and all the other problems that come with it. You can get the crankshaft turned like .10 under, 20 under, etc. and get the bearings that coincide if it isn't that bad (mine's totally wasted) and basically rebuild the bottom end. I am just going to get Chester's freshly built 2.8 and he is going to a V8. I learned a valuable $2500 lesson, NEVER take a stranger's word on something that you can't visually inspect. 
so it was a good thing.
