slackett66

Regarding Spun Bearings and my stock crank. How far gone is gone?

Just finished the teardown of a L98 that I plan to drop in my 305 powered '89 T/A. All was perfect until, of course, the oil pan came off. Found 3 rod bearings, 1 main bearing and 2 cam bearings spun.

The gory details....
The rod bearings. One on the first journal and both rods on the second journal (from the front) were spun. They were clearly spun because the tangs were gone. However, all the bearings were fully intact, had no signs of pounding or damage, only the tangs were gone. I only discovered this AFTER pulling the rod caps. With the caps in place, there was NO play between the rods and the crank. The rods and caps do have linear scoring. There was so little play, I doubt the previous owner was even aware that he was so near disaster.

The main bearing. I say spun, the tangs were still there but barely. Seems they were near failure. This was in the 2nd journal from the front, in the same area as the spun rod bearings.

The Block . I lifted out the one questionable bearing, the cap and block are perfect. No scoring whatsoever. All the other bearings were fully seated, I didnt pull those out yet, all looked fine.

The Cam. Two of the Cam bearings were rotated so that the oil holes were blocked. They were fully intact and there is minor scoring on the Cam journals.

My concerns.
Pistons, Im going to replace then anyway, no worries there.

Cam, obvious, fully intended to pitch the stock 773 cam for a mild upgrade.

The block, cylinders look fine, no scoring, hone/bore as needed and move on.

The crank is the problem. Can scoring on the rod journals be turned or polished out? The journal with the 2 bad bearings has a noticible difference in geometry, caused be the 2 rods operating at opposing angles will free spinning bearings.

I know the machine shop will have their idea of how to proceed. But, has anyone ever have a similar situation? Hadnt planned on spending a fortune here, just a fresh mild rebuild.

sofakingdom

iTrader: (1)

Cranks can be turned; as long as any gouges aren't too deep or the whole thing worn too far off center. But, NBD regardless; it's just an old stock cast crank, nothing particularly worth preserving. You can buy another reground one for about the same cost as regrinding that one, except you'll have to pay a core charge which should be like $25 TOPS.

My main concern in all you describe, would be the rods. Rod bearing failure is INEVITABLE if the rod is even SLIGHTLY damaged, which IT IS if the bearing has spun in it AT ALL. Frankly, I would throw those in the trash and get new ones; costs about the same as "reconditioning", which is what we all used to have to do in the bad old days before replacement ones became so widely and cheeeeeeeeeeply available. Makes no sense to work over old trashed-out stock junk any more.

Sounds like the PO ran it without any oil in it.

slackett66

Sofa... My thoughts exactly. Originally intended rings, bearings and gaskets but it quickyly went to other direction.

Once I saw the spun bearings, I knew I was in for at least a new set of pictons and rods.

A testiment to regular oil changes, thats for sure.

urbanhunter44

iTrader: (3)

I agree with sofa 100%

If you have to buy a new crank anyway a cheap cast 400 crank is nearly the same price