thrust and main bearing failure

[1987noblegn]

the motor only has less than a thousand miles after rebuild and already the thrust bearing is shot and one of the mains is mashed and started to wear and crank is grooved. rod bearings look great. looking for any input on what caused a failure already. we took apart motor trying to diaganose low oil pressure problems and found gobs of copper flakes in pan. the tranny is also doing what my tranny guy calls a flare between 2nd and 3rd and beleives it is a pressure problem. ive heard that can cause thrust bearings to go out. can this cause more? hoping to be able to mill the crank again and replace all the bearings but also want to prevent this problem again.

 

[turbofabricator]

If the crank was already machined . 010" they usually "touch" the thrust surface to verify it is straight. By touching the thrust face with the grinding wheel it creates a saw tooth effect and it will chew itself into the bearing causing failure. I hand polish the thrust surface with 600 grit and then 1500 grit paper and then do a final cleaning. It is also possible that the converter is ballooning causing the failure, too. The other possibility is that the thrust cap was not seated during installation. You need to WHACK the crank backwards then forwards after sniffing the bolts to around 20 ft/lbs. By using a big dead blow hammer. What was the bearing clearance on install? How was it verified? Were all the parts cleaned and cleaned again?

 

[bison]

I'd Ck the converter and the charge pressure first. I wouldn't want to see over 50psi in the cooling circuit.

 

[TurboBuRick]

The builder should be able to tell you whats up once he gets it torn down. If not I would look for a different one.

RL

 

[DailyDrifter]

Im going with torque converter ballooning

 

[TurboBuRick]

That's a good possibility but without physically checking the motors clearance's it's all speculation.

RL

 

[Nick Micale]

Is the converter and trans the same as before the rebuild?

If so, the issue will with be with the block, caps or crank.

Did you receive a spec sheet on the short block with all clearances that were set and checked after machining and during assembly?

First item to have checked now is the crank bore alignment and tolerances.

Unless you were doing some awesome launches and high RPM runs in that thousand miles, I cannot imagine a converter ballooning, especially a stock one?

You will also see a mark on the flexplate if the converter has "pushed" hard enough to cause that damage.

 

[jdpolzin]

A few things:

1. Do you run a transbrake? If not, how many times have you brake boosted it? Easy way to wipe out thrust by trying to spool a turbo.

2. Balooning converter

3. Was the block line honed? Too many people try to get by without line honing the crank bore and the crank isnt sitting stright to begin with.

4. What were your clearences on your mains? Out of whack clearences only gives the crank the ability to "bounce" around in the block.

5. Detonation.....this will kill anything and cause your caps to move.

 

[bison]

If the radius on the mains wasn't somehow blocking oil flow through the bearing which is doubtful on the thrust main and there was proper clearance when it was fired then there is
only one likely cause. Forward pressure from the converter charge. I've seen improperly installed bearings where the halves ddnt have proper alignment, wasted mains and many other issues and the thrust was not a problem even with all that working against it. If converter charge is questionable then I'd be looking there first. You will be verifying all the other clearances on re-assembly. You can't skip the charge pressure even if you somehow find out there was a maching issue that could be a contributor. Line honing won't correct a set of caps that was improperly installed either.

 

[haywire4130]

when i tore my motor down this past fall, the thrust face on the crank was worn about 1/8" (eight inch!). i checked the runout with a dial indicator and the nose where the balancer mounts had about .006" of runout. i talked to a few machinists and they said this wobble could cause the crank to walk forward with enough force to wipe the thrust out pretty quick (previous owner had motor rebuilt 800 (hard) miles before blowing it up and selling to me). i replaced the crank with a used std/std and measured it the same way, it had about a half-thousandth of runout. no issues with 6k on it and counting.

 

[1987noblegn]

sorry for my delays. i really appreciate all the info. ill try to answer everything. clearances were never manually checked. machine shop said clearances were within 2 thousandths. crank was turned 10 and rods 20. block bored 40 over. line bore checked. the crank was apparently bent then straightened. machine shop installed the mains. when i received block back the cam and crank were installed. i installed the rods. i believe i have an anti balooning plate on the torque converter. it is a precision 3300 stahl. but i do not have a transbrake only a line lock. converter and tranny are the same. i just heard back from the machine shop today and they told me that the crank was bent again! this time by 8 thousandths. im thinking about a new crank.

 

[haywire4130]

;-) sounds like a no brainer... Go with a new forged one, .010/.020 and "straightened"? I would have fired it in the scrap pile! Also, if you have a competent machinist doing your lower end work he should hand you a sheet with all the clearances when it comes time to square up!