Researching options for engine rebuild in my 03 2500HD

[GeoffP]

I've bought a really nice high mile 03 2500HD crew cab 4x4 with an LQ4 recently. It runs good but I'm thinking I'll be rebuilding it sooner than later due to the mileage, 300,000 miles! It doesn't leak or burn oil at all and it has decent power but as Tim would say on Home Improvement, "I want more power!" The engine has 317 heads on it which I've read flow similarly to the 243 heads but they're low compression heads. It's a completely stock LQ4 so what low(er) cost changes will give me the best bang for the buck? I've had long tube headers suggested to me but I'm not sure how the exhaust could be setup to clear the 4x4 gear. My primary use for the truck will be as a daily driver and to tow a car trailer, 6300 lbs camper, and our boat to the lake. So what say you - what suggestions do you guys have to make it better??

[Z06vet]

I'd look into some torque cams for it. I'll be doing a cam swap soon on my 07 2500HD. Looking into long tubes as well, as they seem to help the bottom end some. These motors could use more bottom end torque given their weight. Add a trailer & it becomes a necessity. At 3500rpm- up it will pull just about anything, but thats not practical. Throw a tune at it to get rid of the torque manangement- that alone makes a noticeable difference. I'm planning on staying with 87 octane, but if you wanted to run 93 you have some more options with compression if you decide to rebuild. Scott

[GeoffP]

Thanks for the input. I agree that it really could use some bottom end torque. I noticed that when pulling my 6300 lbs camper a few weeks ago. Do you know if the retail box programmers do anything with the torque management or do I have to go with a custom tune to turn it off? I also want to stay with 87 octane so I'm not interested in high compression changes.

[Z06vet]

It's been a while since I used a hand-held. I cant recall. My tuner uses efi live and the options are limitless. I have a 6 speed auto and it shifted so early, i'd be in 4th locked up by 25mph. I had him remove tq conv lockup 1st-3rd and bump the shift points a bit, both up & down. Firmed up the shifts a bit as well. Costs more up front but is cheaper in the long run if you plan on making changes. Fuel mileage went up slightly, about 1-1.5 mpg improvement.

[jakespeeds]

This might be a little more than you were looking for but I have an 02 Sierra 2500HD 4X4. Mine has the 8.1 and the Allison trans. I see the engines around for sale and the transmission pop up from time to time. I have never run out of power. From time to time I have to tow a 12K pound trailer and it does it no problem. Pop a 8.1 and the Allison in there. Call it done.

Jake

[GeoffP]

Yah, I'm not interested in an 8.1 swap. The 6.0 can be made to produce the torque I want. It's just a matter of my making the decision which path to take to get it, either external bolt on's, turbo, or cam/heads. I'm leaning towards external bolt on's unless my IROC sells for a decent amount. If my IROC sells for a decent amount I'll go with a front mount turbo and have it tuned by someone who knows what they're doing.

[John@Texas-Speed]

IMO the best things you can do to pick up a LQ4 motor is a good cold air intake, long tube headers, a set of 243 heads and a small cam. The 243 heads will bump the compression a decent amount which picks up power everywhere, especially low end torque. A small cam to match and the motor should be around 500 at the crank, no issue at all. It will remain extremely drivable just more power everywhere. We have a few customers that were looking for towing packages, I sold them a couple packages very similar to this and they were extremely happy.

[GeoffP]

Thanks John. I was hoping one of the shops would pick up on this thread and make some suggestions. Can you PM me some details and what kind of expense this setup would be?

Thanks!

[John@Texas-Speed]

Yes sir I will get a package put together once I get to the shop on monday for you.

[93Polo]

Geoff, A cam and 243s can really pick them up. Another option to consider is forced induction, plenty have pulled trailers with turbos and Maggies/Whipples. A Corvette friend reported picking up mileage with a lil MP112 on his 6.0 GMC pulling the Z06. MP112s do pop up for sale used on Performancetrucks.net.

If I ever rebuild mine it'll get forged pistons, decent rods and a small cam like the LPE GT2-3 and a TVS1900 or whipple.

[GeoffP]

It's been awhile since I brought this topic back up but figure it's about time since my car sold and I bought a 2004 2500HD wreck parts truck for cheap (I just have to go pick it up). I think what I probably will be doing is the Texas Speed 243's, tsp220 cam, full length headers, along with their mail order tune. All of this will go on the 6.0 out of the parts truck with the stock untouched bottom end and I'll swap it complete into my 03. I'm hoping this will get me close to my goal of as much torque as possible without doing crazy mods to the truck since it is after all going to be my DD. I would love to see 425-450 ft lbs of torque at the rear wheels. My only uncertainty at this point is the gearing. I am pretty sure the truck I bought has 3.73's and my truck has 4.10's so I've got the option of either. I know the 4.10's are better for towing but not gas mileage. If I can get good enough torque down low I might try the 3.73's before I start parting the truck out to recoup the purchase. Opinions on the gearing??