What is the max reliable overbore on a LMM block without filling the jackets?

[Gentrysgarage]

As the title says: What is the max reliable overbore on a LMM block without filling the jackets? I searched and found a few threads but by the time there was answers they had degenerated into filling the water jackets and full on sled pulling. It seemed that no one had direct knowledge of the max overbore for an on-road truck. My truck will be built for long distance towing and don't want to fill the jackets. I am leaning towards the delipped LB7 pistons ( if that makes a difference) trying to save some money anywhere I can. Thanks in advance.

 

[shakenfake]

Anybody sleeving duramax blocks?

 

[JoshH]

I don't know of anybody that makes a cast piston any larger than .040 over, so I would say that's about it for a build like you're describing.

 

[Gentrysgarage]

Anybody sleeving duramax blocks?

Good question, I am worried that one of the blocks I have has some deep scoring as the PO continued to run the motor for an hour every other month and I think there is deep scoring in just one of the cylinders because of this. This motor was rebuilt just 40K earlier (according to PO) and everthing else SHOULD (in a perfect world) be in great shape to reuse with a seal and gasket changes.

I don't know of anybody that makes a cast piston any larger than .040 over, so I would say that's about it for a build like you're describing.

Thanks JoshH for the answer, so to change my question anybody run the .040 pistons on the highway?

 

[gmduramax]

Good question, I am worried that one of the blocks I have has some deep scoring as the PO continued to run the motor for an hour every other month and I think there is deep scoring in just one of the cylinders because of this. This motor was rebuilt just 40K earlier (according to PO) and everthing else SHOULD (in a perfect world) be in great shape to reuse with a seal and gasket changes.

Thanks JoshH for the answer, so to change my question anybody run the .040 pistons on the highway?

Got about 125k miles with .040 around 1000ish hp the block is half filled

 

[Fingers]

0.040" over is fine. Especially for the daily driver.

 

[ikeG]

You can sleeve a Duramax. Always stick to the smallest possible bore size, but like mentioned there really aren't on-the-shelf options for going very big anyhow.

Sent from my SM-G960U1 using Tapatalk

 

[Bdsankey]

0.040" is a fine overbore, especially if you aren't going to be aiming for any big HP.

 

[Gentrysgarage]

Thanks guys for the replies, It is reassuring was just worried that all I had read in my searches was .020 and then filling the block.

 

[kidturbo]

Have ran a .040 over at 700hp in high RPM marine build without issues for several year. From what I've learned, would certainly spend $500 for a good used block before attemting to sleeve one if it comes down that choice.

 

[Gentrysgarage]

Thanks for the reply, I hope both blocks I have don't need sleeves....

 

[turbovan]

Had a friends melt down due to a bad tune, so they sleeved the one gouged up bore.