Scored Crankshaft Bearing

[Dan D]

I finished tearing down the motor out of #410 this weekend. Everything looked decent. Clearances on the bearings were getting kind of high and rings weren't sealing in the cylinder. The one problem I did find was the at the rear main cap. I pulled off the cap and inspected the crank journal and bearing. The cap side of the bearing had a groove that could be felt with my fingertip. The crank looks pristine.

I'm assuming that the bearings are much softer than the treated crank journal and this is the intended failure mode - bearing craps out and spares the crank.

I mic'd the crank journal 4 places across its length and there is no abnormal or uneven wear, no scratches, no grooves. Is there anything to worry about or is the crank just fine?

 

[G]

I would send it in or take it to a crank specialist to be sure. Is this a race engine or dd? That way you can have everything checked out including but not limited to blended radii, thrust wear & alignment, sealing diameters, nose ends & balancing. If it needs to be polished be sure to check with the bearing manufacturer (if they are aftermarket) to get their requirements for surface finish & hardness specification.

 

[BoostedAWD91]

+1 do u have any pics of the bearing?

 

[Dialcaliper]

Is the wear mark in the bearing right down the center? If so, the oiling hole in the crank might have a burr on it. You're correct in assuming the bearing is meant to go before the crank.

The wear marks are probably from startup rather than wear from high loads unless the oil passage in the block is gunked up. Make sure to clean those out well.

I'd check out the oiling holes on the crank for anything resembling a rough spot. If you have the crank out, it wouldn't hurt to have it checked and magnafluxed for cracks by a machine shop. They can also tell you if it could use a fresh polishing.

 

[Dan D]

Thanks for the input guys. The wear is in line with the oil hole. I don't feel a burr on it, but I'll be sure whoever does the refresh on the motor takes a look at the overall condition first.