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6.5L Turbo Diesel 1992-00 6.5TD - Discussion forum for the 6.5L engine.

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  #1  
Old 04-25-2018, 11:25 AM
JeepSJ JeepSJ is offline
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Default Cracked Navistar block

Got a call from the machine shop yesterday and had to go see this for myself.

Yes, this is a cracked Navistar block. Main web. Interesting that the crack is starting at the top and working its way down. There are big stress risers on the top of every main, apparently from something in the machining process. I'll get more pictures when I go back. I had 2 blocks and the plan was to build the second block for my dually. I guess the dually gets a Cummins now...

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Old 04-25-2018, 04:39 PM
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Sorry to see the big crack.

These blocks and the AMG blocks have a buttload of stress risers.

I spent nearly a day "DEHORNING" my AMG block.

I chamfered all the bolt holes, smoothed off every sharp edge, used a tiny carbide ball and removed the sharp corners in main cap registers of the block.

Smoothed off the lower edges of the cylinders and chamfered the oil passage holes in the main bearing saddles, including the oil squirt holes.

Getting at the top end of the squirt holes is a beotch but a small ball in the angle die grinder did it.

I chamfered the top of each cylinder bore with a 45 about 3/32 wide to kill the stress riser and allow the rings AN EASY ENTRANCE

After the bores were chamfered I hit them a quick lick with the bottlebrush hone to make things real smooth.

Also knocked the sharp edge off the fore and aft bores of the mains too.

NO SHARPIES
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Old 05-04-2018, 11:56 AM
ronniejoe ronniejoe is offline
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That's not lined up with the bolt hole, either. That's unusual.
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Old 05-07-2018, 09:31 AM
JeepSJ JeepSJ is offline
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Quote:
Originally Posted by ronniejoe View Post
That's not lined up with the bolt hole, either. That's unusual.
Stress riser at the top of the web. The block is loaded with them.
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Old 05-22-2018, 02:57 PM
JeepSJ JeepSJ is offline
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Machining the "good" block (the not cracked one), they got about 020 over and hit a pocket on a cylinder wall that looks like a casting flaw with what looks to be pin holes in the metal.

After a discussion about the possibilities and "what ifs" it was decided to be prudent and sleeve that cylinder and hope nothing shows up in the other cylinders as we bore them.




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Old 05-23-2018, 08:12 AM
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Done right, sleeves are a good save for an otherwise good block. Our 6.5TD Project engine ran 300k while it was here with #8 having a cast iron sleeve.

Quote:
Originally Posted by JeepSJ View Post
Machining the "good" block (the not cracked one), they got about 020 over and hit a pocket on a cylinder wall that looks like a casting flaw with what looks to be pin holes in the metal.

After a discussion about the possibilities and "what ifs" it was decided to be prudent and sleeve that cylinder and hope nothing shows up in the other cylinders as we bore them.




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Old 05-23-2018, 10:29 AM
JeepSJ JeepSJ is offline
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The boring machine aligns to the deck and bores 90 degrees to the deck. We already verified that the deck is parallel to the crank. The existing bore was about 008 off from being perpendicular to the deck and crank. So far, these Navistar blocks are not impressing me.
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Old 05-23-2018, 11:38 AM
ronniejoe ronniejoe is offline
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Quote:
Originally Posted by JeepSJ View Post
The boring machine aligns to the deck and bores 90 degrees to the deck. We already verified that the deck is parallel to the crank. The existing bore was about 008 off from being perpendicular to the deck and crank. So far, these Navistar blocks are not impressing me.
Did you verify that one deck is perpendicular to the other?
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Old 05-23-2018, 02:34 PM
JeepSJ JeepSJ is offline
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Originally Posted by ronniejoe View Post
Did you verify that one deck is perpendicular to the other?
That is a great question. I do not know if they measured that.
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