BBC Thrust bearing

Who has seen a thrust bearing delaminate like this before.
.008 clearance. Marks both sides upper and lower.
Clevite coated

 

Need more info on the combination. Torque converter or clutch? Lots of people will help but they are going to want more info about the combination.

 

Morning,
this combination is in a marathon jet boat.
Steel flywheel then a splined drive shaft to a jet unit. The shaft slides freely.
No converter or clutch.
The motor, boat, mounting system, jet unit has run/raced for several years. During this time there has been several engines either swapped or freshened. In this case the engine had been rebuilt with a new billet crank but same block, rods and heads etc. Engine is 5 hours old.

If you look carefully at the picture there are no radial scores only light marks which are normal after 5 hours of running. Its almost looking like the radius of the rear main journal could be touching-but it doesnt no where near it.
Any thoughts would be helpfull.

 

very important for bbc forever is put a slight chamfer on the mating edges of the bearing to get oil to the thrust faces

 

What about incorrect radius on the bearing?

 

Wonder if the prop is pushing hard against the crank as its pushing the water? When you back off the throttle, then the water is probably pulling it back wards. Both movements may be smacking the crank backwards and forwards. Maybe try setting your crank endfloat way tighter.

 

Jet boat no prop

 

How does other side look?

 

How do the corresponding crank surfaces look?

I gather this all started after a new crank?.........

What brand bearing are you using?

Is this affecting both the front and rear thrust surfaces?

 

Thanks for the questions:
Bearing is a coated Clevite.
new billet crank. Winberg.
Both sides of the bearing (front and rear) upper and lower have been affected.
Jet unit with a splined sliding shaft.

I think if the crank float clearance was tighter it would have marked the crank and started showing radial scores on the thrusts of the bearing with the material escaping.
Im still surprised it didnt score the thrust faces with the bearing fragments that would have been pushed out radially out with the oil flow.

 

Another possibility is it is just a bad bearing (like didn't pass QC at the factory) The way it is delaminating right at the root edge looks suspect to me. Maybe try replacing it with a fresh bearing & run it some more?

Chris Saulnier - Team Tigges
Mechanic Falls, Maine

 

thats the plan