02 LB7 Build

GMCSierra17028569

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Nov 9, 2023
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Hey there,

I’ll post the long story and then the questions at the bottom so if you’d like to help me with the questions then they’ll be available all the way down.

Okay, so I just got my first diesel. It’s a 02’ 2500 Duramax with about 326,000km on it all stock other than some wheels and tires. I actually know nothing about it other than it’s a 2500 extended cab LB. My family friend has the ability to buy salvaged vehicles from the insurance company and he got that for super cheap. It had hit a deer and knocked the rad out and everything on the front passenger side. Other than the rad and battery mount the rest is cosmetic. I haven’t seen it in person yet but when he offered it to me for the price he did I couldn’t refuse. Now this guy knows a lot. He’s built a very successful business rebuilding diesels and I trust his word 100%. He’s gone through it and sent videos of it running (after straightening out the rad) and it appears to run strong with no blow by or anything noticeable to the eyes or ears. It was grandpa owned and it had a great service record.

I don’t have the need to repair the body nor do want to really. What I do have is a large supply of 67-72 GM truck body parts lying around (I have been collecting them for a long time with my grandfather) and I’m hoping to body swap it onto the 02’ frame and drivetrain. We’re already preparing to shorten the frame and do all that. We’ve done it before with a 02’ 8.1 so I doubt this will be too much different. We’ve done so many 67-72 projects and a 69’ K25 was actually my first truck so the body work I’m familiar with. The mechanical end of things I am not haha.

Now that you’re all caught up, it’s time to get to the point.

What I really want to know is how can I build this truck to be a good long lasting truck with enough power to tow my machinery around? It’ll rarely ever exceed 10,000 pounds as I have a small excavation company. But I do hope it will grow and that means bigger machinery.

That being said, I want to see if I can beef it up to get a higher GVW as well. So if anyone has ideas on how I can achieve that that’d be great.

The other thing is I have a 400-500hp 800-1000trq goal while still being reliable and a good DD/tow pig.

Tell me what you think! I’m excited to do this and I’ll be taking my time to make sure it’s done perfectly. Thanks in advance!
 

2004LB7

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Dec 15, 2010
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You'll probably need to box the frame in to handle the extra power and torque of the Duramax. Especially if you are planning on turning up the power. If you stick to 450 hp and under it will typically last a long time. Depending on the health of the transmission you may need to get it built soon to hold the extra torque.

I don't know the laws in your state but getting a higher GVWR on a vehicle is no small task. I think you might need to get it recertified or re-engineered by a company with the right license to do so. It's been a while since I looked into it but I remember it being next to impossible for the regular joe.

If you can make it work, you might want to keep the same chassis from the Duramax and just put the cabs from one of the older ones on it. That way you have the GVRW and strength to tow what you want and can handle the HP increase you want
 
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GMCSierra17028569

New member
Nov 9, 2023
5
0
1
British Columbia Canada
You'll probably need to box the frame in to handle the extra power and torque of the Duramax. Especially if you are planning on turning up the power. If you stick to 450 hp and under it will typically last a long time. Depending on the health of the transmission you may need to get it built soon to hold the extra torque.

I don't know the laws in your state but getting a higher GVWR on a vehicle is no small task. I think you might need to get it recertified or re-engineered by a company with the right license to do so. It's been a while since I looked into it but I remember it being next to impossible for the regular joe.

If you can make it work, you might want to keep the same chassis from the Duramax and just put the cabs from one of the older ones on it. That way you have the GVRW and strength to tow what you want and can handle the HP increase you want
I’ll be using the dmax frame. We’re just going to be shortening it to the proper length. The problem with it is that the frames usually stick out underneath the cab and it can be a look that isn’t necessarily good haha. I’ll cover it up with some running boards/side steps and if I notch the box supports to allow the bed to sit lower so I can do the same with the cab essentially. The bodywork I’m pretty comfortable with there might be a few things regarding the rad support and front clip that I’ll be looking into eventually but for now I think I have a grasp on it as we did a similar one with the 8.1.

I’m mostly uneducated when it comes to modifying the duramax’s. I’ve been around people who’ve owned them and done some mild work but usually just tuning and deleting emissions. I’ve read about the head gaskets and possible injector issues with the LB7’s and I’m more than happy to get a built trans for towing that’s rated for the 500+ hp. For me it’s just that the power ratings are a little… sad haha.

What’s the opinion on twin turbos for DD and towing? I’ve read it keeps the EGT’s down and because I’m not looking for huge power gains it could be the right fit for me?
 

2004LB7

Well-known member
Dec 15, 2010
6,372
1,733
113
Norcal
I’ll be using the dmax frame. We’re just going to be shortening it to the proper length. The problem with it is that the frames usually stick out underneath the cab and it can be a look that isn’t necessarily good haha. I’ll cover it up with some running boards/side steps and if I notch the box supports to allow the bed to sit lower so I can do the same with the cab essentially. The bodywork I’m pretty comfortable with there might be a few things regarding the rad support and front clip that I’ll be looking into eventually but for now I think I have a grasp on it as we did a similar one with the 8.1.

I’m mostly uneducated when it comes to modifying the duramax’s. I’ve been around people who’ve owned them and done some mild work but usually just tuning and deleting emissions. I’ve read about the head gaskets and possible injector issues with the LB7’s and I’m more than happy to get a built trans for towing that’s rated for the 500+ hp. For me it’s just that the power ratings are a little… sad haha.

What’s the opinion on twin turbos for DD and towing? I’ve read it keeps the EGT’s down and because I’m not looking for huge power gains it could be the right fit for me?
Do you have any experience towing with a Duramax? Towing with 500 hp on a diesel is quite a bit different then 500 hp on a gas rig. The torque curve of a diesel makes it feel a lot more powerful then one would expect. You might want to read up on James' thread on towing with high HP. Additional oil cooling is a must. Or you turn it down for towing

Compounds will definitely help with EGT, responsiveness and drivability. But at the risk of greater chances of hurting your engine. High torque down low, while fun, is hard on pistons, rods and crank. You can help some of this with tuning but that kinda negates the point of compounds over a larger single

If you need injectors, go with SAC injectors and you may never need to do them again
 
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GMCSierra17028569

New member
Nov 9, 2023
5
0
1
British Columbia Canada
I’ll be using the dmax frame. We’re just going to be shortening it to the proper length. The problem with it is that the frames usually stick out underneath the cab and it can be a look that isn’t necessarily good haha. I’ll cover it up with some running boards/side steps and if I notch the box supports to allow the bed to sit lower so I can do the same with the cab essentially. The bodywork I’m pretty comfortable with there might be a few things regarding the rad support and front clip that I’ll be looking into eventually but for now I think I have a grasp on it as we did a similar one with the 8.1.

I’m mostly uneducated when it comes to modifying the duramax’s. I’ve been around people who’ve owned them and done some mild work but usually just tuning and deleting emissions. I’ve read about the head gaskets and possible injector issues with the LB7’s and I’m more than happy to get a built trans for towing that’s rated for the 500+ hp. For me it’s just that the power ratings are a little… sad haha.

What’s the opinion on twin turbos for DD and towing? I’ve read it keeps the EGT’s down and because I’m not looking for huge power gains it could be the right fit for me?
Do you have any experience towing with a Duramax? Towing with 500 hp on a diesel is quite a bit different then 500 hp on a gas rig. The torque curve of a diesel makes it feel a lot more powerful then one would expect. You might want to read up on James' thread on towing with high HP. Additional oil cooling is a must. Or you turn it down for towing

Compounds will definitely help with EGT, responsiveness and drivability. But at the risk of greater chances of hurting your engine. High torque down low, while fun, is hard on pistons, rods and crank. You can help some of this with tuning but that kinda negates the point of compounds over a larger single

If you need injectors, go with SAC injectors and you may never need to do them again
I’ve just been in the L5P’s a lot and I love the way they pull as well as a tuned and deleted LML so that’s where the 400-500hp numbers came from seen as those engines hang in around there. I figured if I can more the less mimic those numbers then I can tune it up to also feel and pull like them without the emissions. I’d be happy to rebuild it all accordingly. The whole rotating assembly will be out and getting inspected as is so if I should plan to add new parts in along the way I’ll definitely do that. I know it’ll cost a lot but it’s an investment for me and my company and something I want to be consistent and reliable.

If I do compounds is there a recommendation? I’ve seen people keep the stock turbos and add a smaller one.

My dad had a 07’ Cummins and he had it done up tastefully. Fuel system, turbo, tune, exhaust etc. Everything was done mildly but it made a huge difference over stock. EGT’s never really broke 1400-1500 if I remember those numbers correctly.

I get the basics but it’s coming down to specifics is where I don’t know much especially of these pre emission Duramaxs.

I’m looking into the BD Diesel Towmaster transmission. Rated for 600hp. Also looking into tuners. The Banks Six gun and the EFILIVE both seem to be more than enough. And I know with tunes you usually regret not just getting “the best”.

I appreciate the lead on the injectors though! I’ll definitely take a look asap. I also read that the turbo piping and intercoolers are a good way to keep the temperatures down. Anything else you got throw it my way lmao
 

2004LB7

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Dec 15, 2010
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Stick with a custom tune from EfiLive. But many have stopped tuning due to emissions laws and lawsuits. So get someone lined up before getting too deep into it
 

2004LB7

Well-known member
Dec 15, 2010
6,372
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It helps. I'm not sure what the laws are in your state but some will require you to smog it at whatever is newer, engine or chassis. If it's pre smog law then probably easy to not say anything and just use it as it was registered