Bearing Failure, What was the cause?

[Sleeper-6]

OK, Here's the story. I recently purchased a used short block knowing the bearings were done. Here's what I found inside. I'm not worried because all I needed was the standard bore block to send off to the machine shop, anything else that I can reuse out of it is just a bonus. I'm just curious as to what you think.

Anyway, who can tell me what went wrong here. It looks like #2 and 3 mains took the worst of it. The bearing in #3 is actually pulling away from the cap as seen in the pics. Some of the damage is from debris, but I'm guessing that occurred after the bearings started to fall apart. There was no metal transfer between the block and caps like you would usually see from detonation. All the rod bearings don't look bad at all. The crank did spin nice and free. I haven't measured the main bearing bores yet to see how out of round they are.

 

[Sleeper-6]

A few more pics

 

[SPOOLN]

That looks like the thrust bearing is whats failed. Could have happened from either a ballooning converter. Or launching with a high stall converter. Whenever you install a high stall converter its wanting to push the crankshaft forward at higher rpm. Higher the stall, harder it is on the thrust bearing surface. The bearing failer could've been prevented if the forward thrust clearence been checked in time.

 

[jhuber]

Charles, has the crank been cut already??

 

[Chuck Leeper]

Don't

That looks like the thrust bearing is whats failed. Could have happened from either a ballooning converter. Or launching with a high stall converter. Whenever you install a high stall converter its wanting to push the crankshaft forward at higher rpm. Higher the stall, harder it is on the thrust bearing surface. The bearing failer could've been prevented if the forward thrust clearence been checked in time.

think so...
The thrust main looks to be the least damaged brg in the set. The coloration on the thrust sides looks to me as it didn't take a beating.
My take is:
This blk has been line bored, and the bores are not to spec.
Improper boring/honing techniques will cause the outer bores to become out of round/oversized, etc, as the block is very short. The boring bar has to be used w/ care, to get all bores the same....
Looking at the damaged area, vs the untouched areas on the shells, leads me to believe that there is waaay too much clearance at the parting lines... thus no damage, compared to the ctrs of the brgs.
Back to hugging my LS1!!!
MERRY CHRISTMAS, all!!

 

[Sleeper-6]

John, the crank was cut .010 in the mains according to the bearngs, I don't remember about rods, I'll check when I get home.

Kinda funny someone would go through the time to line bore the block and not go over size on the cylinders, but anything is possable. The cylinder bores measure out around 3.802 It still had Buick pistons in it, But someone has definately been in there.

 

[Chuck Leeper]

Ah ha! Now the additional info is coming out.. .010 on the mains, and the rods are std??
rods std? The "grinder guy" didn't get a shot at screwing them up. [The rod inserts could have taken a beating from the trash created by the mains...
This info could lead 1 to look at:
A. Poor surface finish.[Polished in the wrong direction, too rough on the belt grit.]
B. Ground out of round?
C. Not really .010 under?

More detective work needed..

 

[Sleeper-6]

I only know what the bearings tell me, I've only owned this motor for about a week. I will take some measurements today and see if we can figure more of this out.

 

[V6 Beast]

think so...
The thrust main looks to be the least damaged brg in the set. The coloration on the thrust sides looks to me as it didn't take a beating.
My take is:
This blk has been line bored, and the bores are not to spec.
Improper boring/honing techniques will cause the outer bores to become out of round/oversized, etc, as the block is very short. The boring bar has to be used w/ care, to get all bores the same....
Looking at the damaged area, vs the untouched areas on the shells, leads me to believe that there is waaay too much clearance at the parting lines... thus no damage, compared to the ctrs of the brgs.
Back to hugging my LS1!!!
MERRY CHRISTMAS, all!!

I agree with Chuck. The thrust doesn't look that bad.

This motor didn't come out of North Carolina did it? I saw machine work like that once from someone there.

Sully

 

[Sleeper-6]

I don't know where this motor originaly lived. But I did pick it up locally. The thust surfaces aren't so bad, but I'm amazed at how the face of The #2 main is peeling apart.

 

[Sleeper-6]

Ok, Here's what I have so far. The rods were also Cut .010. I took Measurements on the main bearing bores and they're all on the loose side. #2 has some goofy measurements because the cap does not seem register properly in the block, It drops right into place and has some play. Not sure what happened there.

Here's the measurements I got. The numbers represent the bearing number. The letters being the position inthe bores. looking at the front of the block with it upside down "A" would be between 4 and 10 o'clock, "B" would be between 6:30 and 12:30, and "C" between 8and 2 O'clock.

..............A..................B................C
1-------2.6877------2.6882------2.6878
2-------2.6894------2.6886------2.6860
3-------2.6885------2.6896------2.6887
4-------2.6883------2.6885------2.6882

 

[TURBOELKY]

somebody needs to shoot the machinest. Or shoot the builder for not uusing plastigauge or a mic. to take measurements.....

 

[Chuck Leeper]

Holy Moly..

somebody needs to shoot the machinest. Or shoot the builder for not uusing plastigauge or a mic. to take measurements.....

Batman! Turboelky hit it on the head! There's no cure for "stupid", and this is a good example.!
Looking at the differences on the dims, it's obvious why the brgs are beat up..[Specs are 2.6870 to 2.6880.]
Like I said before, incorrect use of the hone will cause all kinds of whacked bore sizes.:frown: [Maybe, the caps were cut, and the line bore never done].
As for #2.. it's not only .0005 to .0007 OS, it's way out of round by [A&C dims] .001, and it's .0016 OS, to boot. No wonder that brg is caved in,, Likely had zip for crush. It would have been interesting to see what clearances were B4 this engine was started.
The cap is likely caved in, due to being beat on, and thus contributes to the dim being whacked. Also why it's loose in the saddle..
Looks like it's time for steel caps on all positions, and a line bore by someone that knows WTF is going on..
Hopefully, the "resident moron" didn't do the rods, and they may be OK..
Given the beating these brgs took, it may be they had some detonation added in, and the engine was pulled before the caps had time to transfer metal...
Best deal?? Get your $$ back, and look elsewhere for a block.. No point in trying to "make a silk purse out of a sows ear"..<< Old, folks saying..

 

[Sleeper-6]

I was planning on doing a girdle, and possibly the center mains too. ( I know, overkill ) So I would be looking at a line bore anyway. Is it possible to get the front and rear mains back to spec, or can a grab those two caps off another block?

The rod bearings look pretty good, maybe some marks from the crap in the oil, but no crazy stuff like what went on with the mains.

 

[Sleeper-6]

Hello................Anybody ever fix an issue like this?