Bob, that’s puzzling.

What brand aftermarket crank do you have? Is it still a stock stroke?

I’m having trouble picturing how the converter can cause thrust issues. I presume this is on the back side of the bearing and the crank has been pushed forward. The flex plate bolts to the crank with no real way to move. On the last auto I installed, the converter was pushed back on the input shaft as far as it would go while out of the car. Once the slush box was bolted to the engine, the converter was pulled forward to bolt to the flex plate. What am I missing here?

TKOPerformance wrote:

Its not uncommon for a converter to cause thrust issues, because if the converter is in effect slightly too long it is jammed in there and applies force to the weakest link in the chain, which is the soft thrust bearing.  BUT, why is the bearing okay and the crank undercut?  That's what makes no sense. 

Thanks for the explanation.

This brought up another question for Bob, what brand bearings were installed?
 

Looks like the counterweight on the crank was forced or dropped on the side of the bearing when installing it as evidenced by the two dented areas on the edge of the bearing. That probably cracked the bearing.
The rest could be due to the damaged bearing having less clearance, or your torque converter theory.

TKO
Some internet searches say that these Red China cranks have poor machining on the sides of the crank journals which slings the oil out. Even if true, it wouldn't account for the thrust damage on mine.

Bolted
The crank is a Scat 393 stroker.
The flexplate, as its name implies, flexes. If the snout on the converter isn't machined deep enough for the recess in the crank end, it will bottom out and push the crank forward. If the converter balloons at rpm, it will also push the crank forward. I had no idea these were common problems till I had mine.

TKO
The bearing is not ok, it's just not as bad as the crank  I agree that the crank wearing more than the bearing makes no sense.

Bolted
The bearings are Clevite 77 P

Bullet Bob
See? You are one smart cookie. No explanation needed.

MS
My brother and I assembled the motor short block, clearanced the block in a few spots where the rod caps interfered at the oil pump mount and cylinder skirts, fly cut the piston tops, and thoroughly cleaned the block and parts. Before final assembly I installed a new set of bearings. While the crank was R&I'd several times duriing the build, it was never dropped, or dropped onto the bearings. I just had my hands on the damaged bearing and there are no dents on it. Not sure what area of the bearing caught your attention, maybe the pic below is it. Sometimes pictures are deceiving. Even if the bearing was damaged, I can't see how that would cause the thrust force needed to cause the wear to the crank. An engine alone does not make thrust.

This piece of bearing was separating from the thrust side which I pulled away before taking the picture.

Yeah, I'm stumped on that one.  How cast iron or steel wears more than babbit is beyond me.  I'd expect at the very least to see nothing but copper on that side of the bearing. 

Was any iron material embedded in the thrust bearing surface?  I'm wondering if it's getting the particles embedded and then working on the crank like oil lubricated sandpaper.  That would explain why the bearing isn't as damaged as the crank I suppose. 

Two questions. How was the main cap orientated on the block- where the bearing tangs on the same sides on all caps . Lastly was crank endplay checked before or after the harmonic dampner was installed, and is there any wear on the back side of the timing chain gear?

MachTJ wrote:

Two questions.

How was the main cap orientated on the block-

-Correctly  With the arrows pointing forward.

where the bearing tangs on the same sides on all caps .

-Yes, however with that tang metal forced back to the crank, I don't think you'd be able to rotate the crank if you were able to torque down the caps.

Lastly was crank endplay checked before or after the harmonic dampner was installed, and is there any wear on the back side of the timing chain gear?

-Yes, it was. The endplay was checked both before and after I installed the dampner.

-No damage or contact marks on the front cover.

rpm wrote:

,          I know, put a 5 speed in it.           )

My thoughts zak-lee!! J/K
Just the leak was the only indication you had sump-thin wasn't right?!!
If so............that's scary!
6s6
 

I've "seen" stuff get spray welded(years ago!) butt know nothing about how it happens. I think there may be a little"black magic" involved!
What's the plan?
Spray weld/repair the crank and  re install?!
How's the quality/cost of a new stroker crank?!? (Like Eagle?)
You kinda know what you got now....with new crank that advantage is gone.
Was the converter a "trick" piece or  FoMoCo?!
From what I've read/heard most everything is Chinese-made....even if it sez Made in US of A.! (made there...machined here?!)
Sounds like you have some purdy-smart folks(and friends) on your side....That's a huge +! Hang-in-ther and let us know what happens.
6sally6

6sally6 wrote:

I've "seen" stuff get spray welded(years ago!) butt know nothing about how it happens. I think there may be a little"black magic" involved!

Black magic indeed. When I hear about stuff like those crank welders, I wonder how they got thinking to that point. Who even would think of spraying granulated flux into an arc???

What's the plan? Spray weld/repair the crank and  re install?!

Yes, Weld the damaged area, polish the journals, then check and if they're within spec, if not, take them to .010 under.

How's the quality/cost of a new stroker crank?!? (Like Eagle?)
 
At least twice as much as a repair. Quality, who knows.

You kinda know what you got now....with new crank that advantage is gone.

Ya, I'm confident the repairs will be fine. That is, up until I fire it up.

Was the converter a "trick" piece or  FoMoCo?!

Ya trick. It was the trick stock one delivered by Henry.

From what I've read/heard most everything is Chinese-made....even if it sez Made in US of A.! (made there...machined here?!)

That's also what I've read.

Sounds like you have some purdy-smart folks(and friends) on your side....That's a huge +! Hang-in-ther and let us know what happens.

Well, they're smarter than me, so...
I'll probably only let you know if all goes well. If not, I've got a 460/C6 combo I need to do sumpin wit.

6sally6

MS wrote:

These are the marks I saw.  If you installed the crank yourself, that is not likely the issue.  Hope your problem gets worked out.  I have the Scat forged crank.  Is yours the cast or forged one?

Well, now that you point those out, yes I do see your point of view.

My Scat crank is cast. Shallow pockets. When I was first looking into the Scat crank, 393 was it. One day I googled scat, HOLY CRAP! I must have led a sheltered life by what I found.