Cause of crankshaft wear

[4eighteener]

What I see is two of the same shells, All very well they were marked upper and lower BUT those should of had the tangs different to each other, Stuff does get labeled and packaged wrong including wrong size marked bearings, compare this pair to the other sets. 1/2 of this set was cutting into the radi.
View attachment 1716360599

Not sure what you are talking about. Both the upper bearing shell tang and the lower bearing shell and tangs are correct. The bottom rod cap has a bevel that matched the rod's bevel, both tangs were in the tang locator.
Yes, the bottom tang looks flattened compared to the top, not because it was installed wrong, but probably more so from the hammering once the gap opened up.
I can post pictures of the rod, caps, and bearings if you like now that I got it completely disassembled.

 

[4eighteener]

Assembled and torqued rods and bearings are not concentric. There is a measurable amount of out of round purposely built in to the rod and bearings. They pull in to round when running.
What was the assembled clearance on that rod/bearing? Saying “I plastigauged them and they were all in spec” is not good enough.

Every rod bearing had a clearance of.0015 if my memory is correct. I only remember that because like I said, I was concerned that waa too tight. Had one been less, I probably would have ordered the .001 undersized bearing clevite offered.
The scat rods were torqued to 64'lb with arp lube on the threads and heads.
Is plastigauge as accurate as a dial bore, no. Is it good enough to point out something is not right, yes.
Some have mentioned over torqueing the rod bolts. That did not happen, I was methodical in my assembly.
Of course my 40 year old craftsman torque wrench may not be accurate, but, they all got the same torque specs..
I assume scat designed their big end to be concentric at the required torque. Could I have had one bad rod that wasn't and somehow didn't affect the plastigauge, I suppose.
The purpose of the posting and pictures, was I wanted to know if this type of wear had happened to anyone else, and what the cause was. Apparently not.
So far, I had two responses I considered feasible; the grit coming out of the oil hole in the crankshaft and oozing out the sides,before it affected the upper part of the crankshaft, and the other that mentioned glass beads that break down in size before affecting the upper crankshaft I know no glass beads were around my block, the theory with a different abrasive, perhaps.
At this point I will just consider it unexplainable and move on.
Thanks for all the suggestions!

 

[MV8]

Assembled and torqued rods and bearings are not concentric. There is a measurable amount of out of round purposely built in to the rod and bearings. They pull in to round when running.
What was the assembled clearance on that rod/bearing? Saying “I plastigauged them and they were all in spec” is not good enough.

I've heard this many times over the years but I've never found a reference to it in any service manual. If you have one, I'd like to see it.

 

[nutz]

It reads like a good mystery book
If you ever find out would love to know
Sucz for sure sorry for your troubles

 

[TT5.9mag]

I've heard this many times over the years but I've never found a reference to it in any service manual. If you have one, I'd like to see it.

You will not find a reference in any service manual because it won’t matter at factory power levels, or to any manufacturer or mechanic building driver stuff. All you will find is factory bearing clearance and maybe how to measure it with plastigauge, which isn’t accurate enough to see it. A good bore gauge and an accurate mic will show it if you measure in multiple spots around the circumference.
Steve Morris did a video not that long ago where he measured a set of rods on camera and shows it. I’ll see if I can find it.

 

[PROSTOCKTOM]

There are definitely grooves from debris, but it doesn't seem like the typical 360° grooves. The crankshaft was a new out of the box scat crankshaft

Being a Scat crankshaft it wouldn't surprise me if it had a journal that was machined wrong when Scat put it in the box.

Tom

 

[MV8]

You will not find a reference in any service manual because it won’t matter at factory power levels, or to any manufacturer or mechanic building driver stuff. All you will find is factory bearing clearance and maybe how to measure it with plastigauge, which isn’t accurate enough to see it. A good bore gauge and an accurate mic will show it if you measure in multiple spots around the circumference.
Steve Morris did a video not that long ago where he measured a set of rods on camera and shows it. I’ll see if I can find it.

Thanks for the link. I found a reference from Mahle about plain bearings eccentricity in a concentric split bore and where the checks should be made to use against the manual spec: https://www.mahle-aftermarket.com/media/local-media-north-america/pdfs-&-thumbnails/cl77-1-205r.pdf

 

[Newbomb Turk]

Every rod bearing had a clearance of.0015 if my memory is correct. I only remember that because like I said, I was concerned that waa too tight. Had one been less, I probably would have ordered the .001 undersized bearing clevite offered.
The scat rods were torqued to 64'lb with arp lube on the threads and heads.
Is plastigauge as accurate as a dial bore, no. Is it good enough to point out something is not right, yes.
Some have mentioned over torqueing the rod bolts. That did not happen, I was methodical in my assembly.
Of course my 40 year old craftsman torque wrench may not be accurate, but, they all got the same torque specs..
I assume scat designed their big end to be concentric at the required torque. Could I have had one bad rod that wasn't and somehow didn't affect the plastigauge, I suppose.
The purpose of the posting and pictures, was I wanted to know if this type of wear had happened to anyone else, and what the cause was. Apparently not.
So far, I had two responses I considered feasible; the grit coming out of the oil hole in the crankshaft and oozing out the sides,before it affected the upper part of the crankshaft, and the other that mentioned glass beads that break down in size before affecting the upper crankshaft I know no glass beads were around my block, the theory with a different abrasive, perhaps.
At this point I will just consider it unexplainable and move on.
Thanks for all the suggestions!

It is explainable. It ran out of oil. They wear the crank like that because that’s how it gets loaded.

An accurate .0015 is PLENTY of clearance IF you use the correct oil. For that clearance it would be 0W20 or a 5W20. I run .0020 on my rods and .0023 or .0024. And I run a 5w30 but I’m going to test a 0W20.

If you want to run a heavier grade of oil then you need to open the clearance up to account for it.

 

[TT5.9mag]

Every rod bearing had a clearance of.0015 if my memory is correct. I only remember that because like I said, I was concerned that waa too tight. Had one been less, I probably would have ordered the .001 undersized bearing clevite offered.
The scat rods were torqued to 64'lb with arp lube on the threads and heads.
Is plastigauge as accurate as a dial bore, no. Is it good enough to point out something is not right, yes.
Some have mentioned over torqueing the rod bolts. That did not happen, I was methodical in my assembly.
Of course my 40 year old craftsman torque wrench may not be accurate, but, they all got the same torque specs..
I assume scat designed their big end to be concentric at the required torque. Could I have had one bad rod that wasn't and somehow didn't affect the plastigauge, I suppose.
The purpose of the posting and pictures, was I wanted to know if this type of wear had happened to anyone else, and what the cause was. Apparently not.
So far, I had two responses I considered feasible; the grit coming out of the oil hole in the crankshaft and oozing out the sides,before it affected the upper part of the crankshaft, and the other that mentioned glass beads that break down in size before affecting the upper crankshaft I know no glass beads were around my block, the theory with a different abrasive, perhaps.
At this point I will just consider it unexplainable and move on.
Thanks for all the suggestions!

I agree it had lack of lubricant and likely some trash went through it, but I also think for what we as hot rodders build, and the type of oils we gravitate to, that .0015 is far too little clearance for a performance oriented build. Your statement is also why it’s important to have a build sheet when you assemble an engine. If you ever do have a problem it’s easier to nail down the cause without having to remember all of the numbers.

 

[4eighteener]

Being a Scat crankshaft it wouldn't surprise me if it had a journal that was machined wrong when Scat put it in the box.

Tom

Yeah, I might be hitting you up soon for a good forging

 

[4eighteener]

I agree it had lack of lubricant and likely some trash went through it, but I also think for what we as hot rodders build, and the type of oils we gravitate to, that .0015 is far too little clearance for a performance oriented build. Your statement is also why it’s important to have a build sheet when you assemble an engine. If you ever do have a problem it’s easier to nail down the cause without having to remember all of there numbers.

Yes, i believe your "lack of lubricant " is a more accurate than the previous "ran out of oil" saying.
Lack of lubricant is describing what probabably initially happened to that journal whether debris or starvation. Then some hammering once the gap opened up. I still think the wear pattern is strange, but I have moved on now.

 

[4eighteener]

It is explainable. It ran out of oil. They wear the crank like that because that’s how it gets loaded.

An accurate .0015 is PLENTY of clearance IF you use the correct oil. For that clearance it would be 0W20 or a 5W20. I run .0020 on my rods and .0023 or .0024. And I run a 5w30 but I’m going to test a 0W20.

If you want to run a heavier grade of oil then you need to open the clearance up to account for it.

FWIW, I broke the engine in with royal purple 10w30 break in oil. Perhaps a mistake as I found out later that is a synthetic and perhaps not as good for flat tappet cams.
After the break in I switched to Driven HR2 10w30 and got less than 60 highway miles on it before shutting it down.
When I drained it 6 quarts cam out, so it was never without oil

 

[Newbomb Turk]

FWIW, I broke the engine in with royal purple 10w30 break in oil. Perhaps a mistake as I found out later that is a synthetic and perhaps not as good for flat tappet cams.
After the break in I switched to Driven HR2 10w30 and got less than 60 highway miles on it before shutting it down.
When I drained it 6 quarts cam out, so it was never without oil

You can have oil in the pan and not have enough at the bearings.

 

[4eighteener]

You can have oil in the pan and not have enough at the bearings.

Yes, that would be a lack of oil in the right place, not a "it ran out of oil".

 

[TT5.9mag]

Yes, that would be a lack of oil in the right place, not a "it ran out of oil".

He means that particular journal ran out of oil. Not the entire engine.

 

[4eighteener]

He means that particular journal ran out of oil. Not the entire engine.

Perhaps, but I took it more as a flippant insult

 

[Newbomb Turk]

Perhaps, but I took it more as a flippant insult

It was neither. The journal had either no oil or the oil was so thick it could not get out of the bearing fast enough. It overheats and death is near.

I didn't realize I had to spell all that out.

And the wear isn't strange. That's what it looks like when the JOURNAL is out of oil.

 

[furrystump]

You mention “ nothing that 2000 grit couldn’t handle” I don’t like the idea of using sandpaper on a bearing. The grit gets embedded in the bearing.

 

[4eighteener]

It was neither. The journal had either no oil or the oil was so thick it could not get out of the bearing fast enough. It overheats and death is near.

I didn't realize I had to spell all that out.

And the wear isn't strange. That's what it looks like when the JOURNAL is out of oil.

I have seen journals worn concentrically, never eccentrically, hence my post.
I would suspect if the oil was too thick (10w30) it would have affected all the journals fairly equally.
It appears that journal is fed through the crankshaft from the #1 main bearing/journal.
Since that is not worn, I suspect it was something between the two.
I think a lack of lubricant would wear equally all the way around, so i tend to believe it is probably a combination of things.
Anyway, I have moved on past this and hopefully I don't run into the issue with a new forged crankshaft

 

[Newbomb Turk]

I have seen journals worn concentrically, never eccentrically, hence my post.
I would suspect if the oil was too thick (10w30) it would have affected all the journals fairly equally.
It appears that journal is fed through the crankshaft from the #1 main bearing/journal.
Since that is not worn, I suspect it was something between the two.
I think a lack of lubricant would wear equally all the way around, so i tend to believe it is probably a combination of things.
Anyway, I have moved on past this and hopefully I don't run into the issue with a new forged crankshaft

Why would it wear evenly when the load on the rod is not always the same?

I’ve seen it dozens and dozens of times.

That journal ran out of oil for whatever reason.

My best guess is it was tighter than the rest of them, oil flow was restricted because you need oil flow to cool the bearings and crank and the oil overheated and failed.

That’s why if you want to assemble engines you really need to invest in basic measuring tools.

Dial indicators, a 0-6 inch micrometer set, bore gauge and other stuff like that.

You need to measure every throw and main bearing and then set your dual bore gauge and verify clearance.

When you get under .002 clearance on a 2.125 shaft you don’t have much room for error.

Plastigauge won’t cut it at that point.

 

[4eighteener]

You mention “ nothing that 2000 grit couldn’t handle” I don’t like the idea of using sandpaper on a bearing. The grit gets embedded in the bearing.

Yeah, nah, I don't share that concern. Abrasives are used through engine rebuilding from boring cylinders(well matbe diamonds now)to polishing cranks, and lapping valves. Yes, my response about 2000 grit sounded flippant, but care would have been taken to thoroughly clean any and all parts.
I am not going to reuse them with a new crankshaft.

 

[RustyRatRod]

Why would it wear evenly when the load on the rod is not always the same?

I’ve seen it dozens and dozens of times.

That journal ran out of oil for whatever reason.

My best guess is it was tighter than the rest of them, oil flow was restricted because you need oil flow to cool the bearings and crank and the oil overheated and failed.

That’s why if you want to assemble engines you really need to invest in basic measuring tools.

Dial indicators, a 0-6 inch micrometer set, bore gauge and other stuff like that.

You need to measure every throw and main bearing and then set your dual bore gauge and verify clearance.

When you get under .002 clearance on a 2.125 shaft you don’t have much room for error.

Plastigauge won’t cut it at that point.

That's the only way I've EVER seen one wear that started to or spun a bearing.

 

[4eighteener]

That's the only way I've EVER seen one wear that started to or spun a bearing.

It was probably close to it, judging by the tab, but it hadn't spun yet

 

[TT5.9mag]

Plastigauge won’t cut it at that point

I may have broke my phone punching the agree button.

 

[4eighteener]

Why would it wear evenly when the load on the rod is not always the same?

I’ve seen it dozens and dozens of times.

That journal ran out of oil for whatever reason.

My best guess is it was tighter than the rest of them, oil flow was restricted because you need oil flow to cool the bearings and crank and the oil overheated and failed.

That’s why if you want to assemble engines you really need to invest in basic measuring tools.

Dial indicators, a 0-6 inch micrometer set, bore gauge and other stuff like that.

You need to measure every throw and main bearing and then set your dual bore gauge and verify clearance.

When you get under .002 clearance on a 2.125 shaft you don’t have much room for error.

Plastigauge won’t cut it at that point.

Agreecto disagree