My 6.2 spun the center 3 main bearings. Has this happened to anyone else ? I replaced all the mains with used bearings as a last chance effort,but even though it has good oil pressure the motor knocks pretty bad . I wonder if my bearing girdle had any thing to do with it ? I didn't put it back on,not that it matters at this point.
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Spun main bearings
- Thread starter 6.2 turbo
- Start date
iamdave0887
Here Comes Chaos.....
I'd say knocking would be more of a rod bearing, because that's where most of the downward force from the combustion is. The main bearings i don't think would knock since the crank is just spinning there, and isn't dealing with as much up and down force as the rod bearings are. Granted there is still force as it's transmitted throughout the engine, but i think a rod bearing would knock much easier than a main bearing.
Don't know about the girdle causing it.
The '67 390 i'm working on right now spun most of the rod bearings, and when spinning the engine over by hand quickly with the heads off i could hear the rod bearings slapping around. Dis-assembly showed all bearings were showing lots of copper. One thing that could cause spun bearings is insufficient oil supply. this 390's main saddle oiling holes and the main bearing oiling holes were not totally lined up. This would give good pressure but not good flow as pressure is resistance to flow. When i looked at everything a second time with added light I could see the worst rod bearings were near the misaligned main bearing/saddle oiling holes.
Don't know about the girdle causing it.
The '67 390 i'm working on right now spun most of the rod bearings, and when spinning the engine over by hand quickly with the heads off i could hear the rod bearings slapping around. Dis-assembly showed all bearings were showing lots of copper. One thing that could cause spun bearings is insufficient oil supply. this 390's main saddle oiling holes and the main bearing oiling holes were not totally lined up. This would give good pressure but not good flow as pressure is resistance to flow. When i looked at everything a second time with added light I could see the worst rod bearings were near the misaligned main bearing/saddle oiling holes.
I imagine the rod bearings might be bad also,since it sounds different now than it did right before I changed the mains. It will take a parts motor and maybe align bore to fix this one,kinda a shame since it is crack free. A long time ago when I first got this motor running it clogged an oil filter,and started running funny,ever since that happend it would ocasionly make a funny noise at idle. When I got it running after I o ringed the block ,something seemed wrong ,almost like the motor was getting tight,though oil pressure was good,I cut the oil filter apart and it had aluminum in it,but not clogged. I thought maybe I got metal in the oil pan from grooving the block,but when I dropped the pan there was only aluminum ,from the bearings.
uniquediesel
1/4 mi. Fan
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What does your girdle look like?
Does seem highly likely that you've got rod bearing issues now too. You cannot have failed main bearings and not have the same material end up in the rod bearings. The rod bearings are fed oil from the mains, so any contamination from the mains will end up in the rod bearings.
Since you mentioned you spun the main bearings, that would indicate to much clearance in the main bore, or an alignment issue. Any alignment issue could certainly be caused by a girdle, especially a home-made one. Another good note, a spun main bearing will also return NO oil to the rod bearings normally supplied oil from that main. The oiling hole gets plugged off when the bearing is not aligned with the oil hole in the block.
If you spun main bearings on a 6.2, the block is basically toast at this point as there isn't a good way to correct the align bore on a 6.2 block because of the 2-piece rear main seal. The only way I know of is to find someone who can do a slow-cut align BORE. You cannot hone a 6.2 block because of the seal issue.
J
Does seem highly likely that you've got rod bearing issues now too. You cannot have failed main bearings and not have the same material end up in the rod bearings. The rod bearings are fed oil from the mains, so any contamination from the mains will end up in the rod bearings.
Since you mentioned you spun the main bearings, that would indicate to much clearance in the main bore, or an alignment issue. Any alignment issue could certainly be caused by a girdle, especially a home-made one. Another good note, a spun main bearing will also return NO oil to the rod bearings normally supplied oil from that main. The oiling hole gets plugged off when the bearing is not aligned with the oil hole in the block.
If you spun main bearings on a 6.2, the block is basically toast at this point as there isn't a good way to correct the align bore on a 6.2 block because of the 2-piece rear main seal. The only way I know of is to find someone who can do a slow-cut align BORE. You cannot hone a 6.2 block because of the seal issue.
J
The girdle is 1/8 inch angle iron,and looks like the DSG. I'm not to worried about the rear main seal with align bore. I think I will leave the girdle off the 6.2 ,and probably the 6.5. Bill Heath uses studs,and no girdle in the mains.
Bad crankshaft bearings will pound rather than knock. Makes a noise like piston slap but not quite like bad lifter.
Suspect used bearings have 'crush' problems and be more likely to spin. Also the 'set' they take the the old crankshaft will be different than the new crankshaft. So may have high friction spots and low oil pressure areas in the same journal.
Suspect used bearings have 'crush' problems and be more likely to spin. Also the 'set' they take the the old crankshaft will be different than the new crankshaft. So may have high friction spots and low oil pressure areas in the same journal.
uniquediesel
1/4 mi. Fan
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There is a fair amount of things that he does that doesen't make sense. While the studs might help the cap stay put a little better, they won't really help the block from cracking. The girdle is the right idea, but everything has to be right. The caps have to have the same height, the girdle straight, etc.
chessie 6.5
Member
You've got some rod bearings bad. Spun mains will either block oil to rods or loose so much pressure as to starve rods or pass bearing debris to rod bearings. remember that rod bearing lubricating holes in crankshaft go from main journals to rod journals.