CrankShaft Thrust Bearing Wiped Out, Why?

[Mustang78]

The #3 cap thrust bearing is completely wiped out down to the copper on both sides of it, but mostly the rear of the thrust bearing is completely scraped clean of any bearing material it once had, and also scarred the crank in that spot, does anyone know why this happened the rest of the mains and rod bearings are in bad shape too, especially for being "freshly rebuilt"...but none as bad as the sides of the thrust bearing, the crank was turned .010 under and they didnt chamfer the oil holes so they marred the bearings..same with the rod bearings, thanks for any help

~Mark~

 

[sawbones25]

Who built the motor?

 

[Dmarstroker]

The #3 cap thrust bearing is completely wiped out down to the copper on both sides of it, but mostly the rear of the thrust bearing is completely scraped clean of any bearing material it once had, and also scarred the crank in that spot, does anyone know why this happened the rest of the mains and rod bearings are in bad shape too, especially for being "freshly rebuilt"...but none as bad as the sides of the thrust bearing, the crank was turned .010 under and they didnt chamfer the oil holes so they marred the bearings..same with the rod bearings, thanks for any help

~Mark~

I had the SAME exact problem with my freshly built motor and had to replace the crankshaft AND all the main bearings two times. The only thing that "I" could think of for my car was that the king cobra clutch that I had in it was too much pressure
that forced the crankshaft to thrust forward and cause the wearing issue. After I replaced the clutch with an o.e. replacement it was fine. I only have an adjustable cable and I'm not sure if having a firewall adjuster could've prevented it. I really need an updraded clutch though cuz my clutch slips when at the track.

 

[cobradvm]

Thrust bearings getting wiped out gets real old, real quick. I had two bearings get wiped out. If it had happened a third time the car was going to get parted out, but fortunately it held. Some things to check...
Make sure that the end play of the crank is within recommended limits
Make sure the engine builder has align honed the block
Check there is no forward force on the crank. On an auto this is usually the converter ballooning and placing a forward force on the crank.
Make sure the input shaft of the tranny is within specs - make sure you are using the correct bell housing with the tranny - some folks change out the bellhousing and don't check this. I think it is more of an issue with the 94/95 bell housings used with 87-93 T5s but not sure.
Check the run out of the bellhousing where the tranny fits in - put the dial indicator on the flywheel, with the tip running on the inside of the hole of the bell housing. It shouldn't vary by more than a couple thousands as the crank is turned.
Make sure there is zero tension on the clutch cable. I made sure I could pull the cable on and off by hand - just make sure its tight enough not to fall off! You may need to change your clutch quadrant to make sure this works okay. You may even want to have the cable off when you start the car - my thrust bearing blew within 200 miles of dropping the engine back in.

Good luck - it's a total bitch from start to finish - after the 3rd time I was checking endplay every 100 miles or so for the first 1000 miles before I was able to relax about it!

 

[Mustang78]

thanks guys for the tips, looks like i need a new crank...that 331 is sooo tempting...and i have no idea who built the motor

~Mark~