Duramax Diesels Forum Truck of the Week
Old 01-12-2019, 06:14 AM
reese600 reese600 is offline
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Posts: 9
Default Rod caps??????????????????

Ok, so I'm disassembling my LBZ bottom end to get the crank out so I can get it keyed. When I took the rod caps off, I find they look like the pics below. All 8 of them. This is the first Duramax that I have torn into the short block. In my 30+ years of turning wrenches, I have rebuilt many types of engines and I have never seen rods that look like this. Where the rod separates, any other engine that I have had apart, these areas have always been machined surfaces. What the hell is this? There is no other broken piece of the rod to be found, they look like they are made like this, but it can't be right, can it?
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Old 01-12-2019, 06:25 AM
Blackmax123 Blackmax123 is offline
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That's completely normal.

The rods are made as one piece and they use a method called crackingor split fractured to break the journal side of the rod in a targeted manner while its bolted together. This achieves a precision fit between the rod shank and bearing cap.

It also prevents the bearing caps and rods from getting mixed up and they will only go together 1 way and every rod cap is different.
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Old 01-12-2019, 06:40 AM
reese600 reese600 is offline
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Blackmax123 - seriously, that is how they are made? I was getting ready to tear my other LBZ apart and see if the rods were the same in it.
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Old 01-12-2019, 07:03 AM
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PureHybrid PureHybrid is offline
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A lot of modern engines have rods manufactured in the fracture split manner. Even some aftermarket rods. Completely normal. BUT do not mix them up, and if you attempt to bolt one together with the wrong cap (which will be obvious if you're paying attention) it will ruin the split surface and your rod will be scrap.
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Old 01-12-2019, 07:06 AM
reese600 reese600 is offline
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ok then, I just watched a couple videos on cracked rods, I guess the GM LS engines have them too.
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Old 01-12-2019, 07:22 AM
gmc502 gmc502 is offline
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Originally Posted by reese600 View Post
ok then, I just watched a couple videos on cracked rods, I guess the GM LS engines have them too.
hope your mind is at ease now.cracked cap technology has been around for awhile now,excellent at alignment.
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