Core shift cyl #2

KBMKVIII

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Long story short I made too many horsetorques and the cam gear walked.
Finishing the rebuild now with stg 2 cam, de-lipped pistons and carrillos.
Motor had 261xxx mi on it and was in great shape otherwise.
Decided to bore 10 over even though it was not necessary for the amount of wear in the cylinders.
It’s a good thing I did, bc we found that #2 had a large amount of core shift.
For those who have not heard of this see pic below.

41019aac0811dd1f8fce1f558b2a7fb7.jpg


To correct this issue I had to sleeve #2.
The shift on the bore did not clean up until 60 over.
This is the original motor that the truck rolled out of the factory with in great condition.
It makes me wonder, as I have heard of a few higher hp obs’s crack the block around #2, if there was a bad run of castings from Mexico.
It was not something that could have been caught by an ID micrometer, as the bore itself was well within tolerance.
I feel good about my decision to sleeve it and I’m glad the issue was found.
Has anyone that bored their motors over, run into this before?
 

Peroni

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I don't see how a core shift on a rough casting would lead to a finished bore being out of line. It would either clean up or not. I would say bored out of line better describes this. It would be interesting to know how Navistar actually machined these and what the actual true position on the bore was. To be machined in a fixture on a multiaxis machine to get a single bore that far off screams manual intervention. And that's usually not something done in a production environment. I wonder if that block was kicked out and got some personalized attention to finish it?
 

KBMKVIII

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I guess it all depends if the hone they use just follows the casting bore or is a fixed angle hone?
Either way, it was way t f off.
I know when the machine shop found it, it was during the boring process.
Just makes me curious.
I still wonder if this was a block that fell off the conveyor or not lol
 

KBMKVIII

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Thats a odd one. Hope you straighten it out and get it together soon. Sounds like a fun ride again!!

live life full throttle


I’m hoping so!
It has been quite the process with all of the little issues I have run into along with extremely long shipping times on parts.
But it’s getting there!

ce52a120b34a30d6bd841ac190e17b21.jpg



e8819481c63ce6361a209b68853a56d9.jpg
 

superpsd

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I recall a post at one time about how swamps picks thru blocks ro find the best one to do a long block build from as they stated the tolerances found on some blocks from factory were out of whack.
 

KBMKVIII

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I recall a post at one time about how swamps picks thru blocks ro find the best one to do a long block build from as they stated the tolerances found on some blocks from factory were out of whack.


I would not be surprised at all, that there are many variations from intended tolerances, in production blocks.
Just makes me happy it held together as long as it did.
We’re all 7.3 blocks made in Mexico?
Regardless, the issue was fixed.
I wish I had the money to sleeve all 8 but funds were limited.
 

Lt.Dan

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Amazing there was that much out of whack on a large number of them, and a huge number of them have made 200k, 300k, even 500k miles...
 

Jonnydime

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Amazing there was that much out of whack on a large number of them, and a huge number of them have made 200k, 300k, even 500k miles...

Sub 300hp and 4000rpm probably helped a ton on most of those.
 

lincolnlocker

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Sub 300hp and 4000rpm probably helped a ton on most of those.
Lol. Yeah. When i had my old dually supposedly "built" the first time around, most of the cylinders where either egg shaped or out of line. Lol..

The second time i had it done properly at Morgan's, the cam bore was out of line. Im guessing it was bored out of wack with the "build" the first time. Just like the cam gear was supposed to be welded and it wasn't.

live life full throttle
 

KBMKVIII

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Lol. Yeah. When i had my old dually supposedly "built" the first time around, most of the cylinders where either egg shaped or out of line. Lol..

The second time i had it done properly at Morgan's, the cam bore was out of line. Im guessing it was bored out of wack with the "build" the first time. Just like the cam gear was supposed to be welded and it wasn't.

live life full throttle


It’s interesting because I have not heard of much of this being found during builds over the years.
I can understand the egg shape with the pistons rocking in the bore, but out of line? Crazy.
At least it was found and fixed.
I would rather it be more expensive now then later...
I wish things would have worked out better Lincoln, I know you went through the ringer with the shop you used the first time around.
 

KBMKVIII

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Just to show y’all, this is #2 cylinder that was sleeved.
You can see the lip that the sleeve sits on and where the bore was completely missing the side of the cylinder wall.
And yes, the sleeve has a lip to sit on all the way around.

5106dbf884ac03453ef359c6268ca952.jpg
 

lincolnlocker

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It’s interesting because I have not heard of much of this being found during builds over the years.
I can understand the egg shape with the pistons rocking in the bore, but out of line? Crazy.
At least it was found and fixed.
I would rather it be more expensive now then later...
I wish things would have worked out better Lincoln, I know you went through the ringer with the shop you used the first time around.

Thanks man. But meh. Blessing in disguise.. expensive one but its right now and is still rocking on with the new owner... i think... i haven't heard from him in a while. Lol

live life full throttle
 

KBMKVIII

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Thanks man. But meh. Blessing in disguise.. expensive one but its right now and is still rocking on with the new owner... i think... i haven't heard from him in a while. Lol

live life full throttle


Did not even know you sold it.
Thought a while back I remembered you having it along with your 6.7.
Whoever got it got a great truck!
 

lincolnlocker

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Did not even know you sold it.
Thought a while back I remembered you having it along with your 6.7.
Whoever got it got a great truck!
Yeah. I couldn't give her the love she deserved anymore and lived in another state and didn't have the room for it out there.

Strokersace on here bought it.

live life full throttle
 

Lt.Dan

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Just to show y’all, this is #2 cylinder that was sleeved.
You can see the lip that the sleeve sits on and where the bore was completely missing the side of the cylinder wall.
And yes, the sleeve has a lip to sit on all the way around.

5106dbf884ac03453ef359c6268ca952.jpg

How thick is that sleeve?
 

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