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TronDD,

A spun bearing referes to the crank bearings. Sometime when a bearing has worn to much or ocasionally a engine is assembeled with to much clearence between the bearings and crank. One bearing half (all crank bearings are two pieces) can spin around with the crank and overlap the other bearing half. Thus a "Spun Bearing". This usually will not render the motor unbuildable. The crank will most likely have to be turned and fitted with oversize bearings when reassembled.

FastSS396Man

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Brian

69' SS396 Chevelle
L78 396/375hp
M-21 Close Ratio
Cortez Silver
10 year Resto
It's brand new again!
02' Harley FatBoy, Diamond Ice pearl.
 

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A spun bearing means you pull out from a traffic light and the POS car stalls (engine seizes up) right in the middle of a 4 lane busy highway!
Well, that's what it mean't to me when it happened.

This was just a puddle jumper (76 Plymouth Arrow) but that engine locked up tighter than a bulls ass! When I ripped it apart, one of the bearings was all burned and scored up.

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Bob (Pa.)

1963 Impala 283
1966 Chevelle SS 409
1969 Malibu 307
1972 Malibu 307
1969 C10 stepside 350
1971 Cheyenne 20 3/4 ton
Somebody stop me... :)

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Hi,

Back in 68 I was racing my 68 Z-28. It was during the time trails and I was up against a 440 Mopar. Now, my Z-28 came from the factory without a tach and I don't really know how many RPM I was turning. But at the end of the run I heard a terrible knocking noise and smoke was coming from the oil filler tube. I took it back to the dealer who said, "well, they don't make these things to drive to Sunday school" and proceed to install a new short block under warranty. They said I had, "spun a crackshaft bearing, which I took to mean at least one of the bearings had dislodged itself from it's normal position and turned around, "spun", on the crankshaft. Never did get a tach....sold the car and bought a 67 Corvette. Those were the days!

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R.E. Stancliff
 

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LOL!


I better clear that up. It's not from personal experience. Just a saying. Sheep are friendlier by the way.


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Bob (Pa.)

1963 Impala 283
1966 Chevelle SS 409
1969 Malibu 307
1972 Malibu 307
1969 C10 stepside 350
1971 Cheyenne 20 3/4 ton
Somebody stop me... :)

Looking for Chevelle or Impala parts? Click here:
Chevelle parts for sale
 

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Typically, this happens when the engine is over-revved, but a bearing is said to have spun when the oil film between the bearing and rod journal breaks down and allows serious metal-to-metal contact, which often destroys the surface of the crankshaft rod journal, connecting rod, and of course, the bearing itself. When this happens, the crankshaft will need to be remachined, or ground, to the next undersize, and the connecting rod can usually be resized by milling the cap and rod mating surfaces and reboring the rod end hole. A resized rod is safe to use in a stock engine, but I don't like using them in a performance engine.



[This message has been edited by Randy Mosier (edited 12-13-2001).]
 
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