Looking for a picture and the difference of the LB7 and the later style pistons.

Gentrysgarage

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Dec 1, 2022
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I pulled apart the parts engine and fount it had Mahle pistons one was holed and another had a crack starting. I thought Mahle was the best but the ones in this engine were cracked. I think I read they changed the piston pin design and also wanted to see a pic of the oil ring land and piston pin distance between the 2. Thanks
 

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JoshH

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What are you seeing that makes you think they’re Mahle pistons? They look just like every LMM piston I’ve seen. Here’s a pic of one I pulled out of an 07.
 

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1FastBrick

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Here is a used LB7 piston. Does this answer your question?

For the LBZ/LMM they redesigned the piston and added a pin bushing to the piston. But they also went to a different manufacture to make them.
 

Gentrysgarage

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JoshH, no honestly I am not, this is my first DMax, but the one side says 3851 the other side is 3451 which when I looked the number, it came up with Mahle pistons and they have the coated skirts.
 

Gentrysgarage

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Dec 1, 2022
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Here is a used LB7 piston. Does this answer your question?

For the LBZ/LMM they redesigned the piston and added a pin bushing to the piston. But they also went to a different manufacture to make them.
Thanks 1FastBrick, I was trying to see if there was a major difference in the distance between the ring and the pin, maybe due to compression difference. I wonder if these aren't Mahle pistions which would be better, the delipped LB7 or the Mahle non-forged?
 

1FastBrick

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JoshH, no honestly I am not, this is my first DMax, but the one side says 3851 the other side is 3451 which when I looked the number, it came up with Mahle pistons and they have the coated skirts.
The Coated skirts is standard on the LBZ and up when they changed piston manufactures.

The Duramax pistons are directional I believe because of the oil squirt location and possibly pin offset. You have right bank and left bank pistons.
 

Chevy1925

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Mahle pistons came factory in the LBZ/LMM. they are a very weak design and commonly crack where yours have. Mahle does make a race cast piston that is stronger than the stock LBZ/LMM and debatable if they are stronger than a stock new LB7/LLY piston thats been delipped.
 

JoshH

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Maybe manufactured for isuzu but the ones you can buy from Mahle are not the same.
Mahle makes a couple of different style pistons. They have the OE pistons, and they have the race cast pistons. I’m not sure if the aftermarket stock replacement Mahle pistons are the same as the OE pistons or not. Maybe someone else can answer that one.
 

1FastBrick

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Mahle makes a couple of different style pistons. They have the OE pistons, and they have the race cast pistons. I’m not sure if the aftermarket stock replacement Mahle pistons are the same as the OE pistons or not. Maybe someone else can answer that one.
They are not exactly the same.

The OE Pistons that came in the motors or that are purchased as replacements through the dealer are not the same as the OE Type Replacements sold through the aftermarket division of Mahle. They are 2 separate divisions and due to specific contracts and what not the are not exactly the same. If you look them over you will see different markings on them. Some time even the castings are drastically different depending on where they are manufactured.
 

JoshH

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They are not exactly the same.

The OE Pistons that came in the motors or that are purchased as replacements through the dealer are not the same as the OE Type Replacements sold through the aftermarket division of Mahle. They are 2 separate divisions and due to specific contracts and what not the are not exactly the same. If you look them over you will see different markings on them. Some time even the castings are drastically different depending on where they are manufactured.
That's what I assumed, but since I've never compared them side by side, I didn't want to say for sure one way or the other. For all I know, GM changed to a different manufacturer for OE replacement LB7/LLY pistons after going with someone else for the LBZ pistons. All I know (from what I have been told by trustworthy, reliable sources) is that the pistons GM/Isuzu used to originally build the LB7 and LLY from 01-05 were manufactured by Mahle, and they changed to a different manufacturer starting with the 06 model year (including the 06 LLY).
 

1FastBrick

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That's what I assumed, but since I've never compared them side by side, I didn't want to say for sure one way or the other. For all I know, GM changed to a different manufacturer for OE replacement LB7/LLY pistons after going with someone else for the LBZ pistons. All I know (from what I have been told by trustworthy, reliable sources) is that the pistons GM/Isuzu used to originally build the LB7 and LLY from 01-05 were manufactured by Mahle, and they changed to a different manufacturer starting with the 06 model year (including the 06 LLY).
GM did the same thing on the LS motors. The early ones were manufactured by Mahle and later they switched to a different manufacture when they started coating the skirts then they switched to a floating pin rod. I have pictures of them some where. comparing the underside of the castings and the OE marks on them.

The machinist I used filled me in that they were separate from the OEM and the Aftermarket Replacement pistons.

I am always curious to learn the back story on things.
 

1FastBrick

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I think on the LS, they went from Mahle to Federal Mogul...

But when you compare the OE to the same brand Aftermarket OE replacement you can see the difference in the castings....
 

ikeG

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I think I mentioned it in another thread, but the new go-to piston, according to Jeremy wagler himself, is the mahle aftermarket stock replacement for a LML. Part number 224-3935. Their delipped piston package starts as them now. Wagler along with myself have had almost every set of motorsports cast pistons crack in any level of application. So he went looking for a solution and that's where they ended up. Im putting one together now with those pistons, so time will tell.

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