Thrust Bearing damage - Why?

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360duster

360duster

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Hi Guys,

have got the motor out of my valiant, preparing for big tube headers and another cam. I noticed a lot of crank endplay......around 0,04". the rearmost thrust surface is damaged. I have no clue why this happened....car is auto trans, there is some space between the converter and the flex plate when unbolted, no "pushing" from converter side. I once ran the engine for a short time with a wrong built converter (727 Stator in it, 904 trans) - could this cause such damage?

It´s a scat crank, i alredy contacted them regarding a new crank.....hope it is possible to supply a new one with the info from the balancing sheet. Or is welding / grinding an option?

Thanks, Michael

damagedThrustbearing.jpg
 
What does the end of the crank and TC snout look like?

I had something similar happen and the TC snout was binding in the crank.
 
Here is one thread on here and there are a few others. There is also a link to another thread on here. Have a look and see if there is any clues you find similar.

good luck

Small block crankshaft endplay
 
Was the thrust bearing surfaces worn evenly on both halves of the bearing? 65'
 
ballooning of torque converter ? /I have seen it many times in other peoples products( 454's motorhomes )
 
Do you know what the end play was when the engine was first assembled?
 
tjpatte said:
What does the end of the crank and TC snout look like?

I had something similar happen and the TC snout was binding in the crank.
Click to expand...

converter and end of crank looks fine, i checked if the converter fits into the crank during installation. Initially i used an old used converter that got damaged during my first season with this engine (sprag broke), maybe this is where it started......
 
360duster said:
converter and end of crank looks fine, i checked if the converter fits into the crank during installation. Initially i used an old used converter that got damaged during my first season with this engine (sprag broke), maybe this is where it started......
Click to expand...
Could be from the old TC. Are there any marks from the snout possibly bottoming in the crank?
 
Did you have any vibrations? An out of balance torque converter or driveline vibration will cause that thrust bearing to go out, I had it happen on a 340 once
 
no, never any vibrations. Setup is internally balanced, that´s all i ever used (neutral balanced dampener and flexplate / converter).
 
360duster said:
Hi Guys,

have got the motor out of my valiant, preparing for big tube headers and another cam. I noticed a lot of crank endplay......around 0,04". the rearmost thrust surface is damaged. I have no clue why this happened....car is auto trans, there is some space between the converter and the flex plate when unbolted, no "pushing" from converter side. I once ran the engine for a short time with a wrong built converter (727 Stator in it, 904 trans) - could this cause such damage?

It´s a scat crank, i alredy contacted them regarding a new crank.....hope it is possible to supply a new one with the info from the balancing sheet. Or is welding / grinding an option?

Thanks, Michael



View attachment 1715684665
Click to expand...


Looks to me like the thrust bearing collar is not long enough. See the space between the end of the collar and the block? That looks suspect to me.



THRUST BEARING.jpg
 
hmmm, you´re right. these bearings were supplied with the rotationg assembly, so i did not worry about. Are there bearings with bigger diameter thrust surface?
 
360duster said:
hmmm, you´re right. these bearings were supplied with the rotationg assembly, so i did not worry about. Are there bearings with bigger diameter thrust surface?
Click to expand...
I believe so, think you can run the smaller bearing on a later block, just don't have as much bearing.
 
When your TC is fully seated in the transmission, what is the distance from the ring gear to the front of the case, should be 1 1/4"? When I had my first issue with the snout size I was sent another converter and the stator was bottoming out on the support shaft and I could only get 1 1/8" which had caused some wear on the thrust bearing. I was able to catch it in time and figure out the issue and they redid my TC and all is good now.
 
i think space from flexplate to converter when pushed in trans is around 1/8th of an inch...afaik this is called good. Did not measure the distance to the front of the case.
 
360duster said:
i think space from flexplate to converter when pushed in trans is around 1/8th of an inch...afaik this is called good. Did not measure the distance to the front of the case.
Click to expand...
Ok, that's good. I did the ring gear method as it was easy to measure before I put the tranny in. With all the issues I had I was looking for ways that involve lifting the tranny as little as possible!
 
360duster said:
hmmm, you´re right. these bearings were supplied with the rotationg assembly, so i did not worry about. Are there bearings with bigger diameter thrust surface?
Click to expand...
The bearing supplied works with ur crank. Ur block takes the wider bearing but ur crank doesn’t. So u need to use what the crank needs and that’s the right bearing in there now. Kim
 
Maybe i'm off base here but, you said the Rear Most thrust bearing.........If that's the case then it would NOt be from excessive pressure from the rear of the crank pushing forward.
With that picture i can tell which side is the rear part of the crank.
 
Only going by the photo, but the journal thrust surface looks rough. Some of the early Chinese cranks had quite roughly finished thrust faces & were wiping out the bearing.
 
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