Tremek

Hey guys, somehow over the past few months my house has become 2/3 GM trucks -

I sold my '12 CTS-V (wagon) over the summer and, as we're doing some major house projects, I picked up a very clean single-owner 2003 Suburban 2500 with Quadrasteer (albeit QS is not working - more on that later maybe) for just over $4k and have been having fun fixing it up and tinkering - pictured below:



It was bone-stock when I got it, so I have gradually made a few changes like pulling the intake and doing knock sensors and subharness, adding an aftermarket head unit and a backup camera, fixing minor stuff like blower motor resistors, upper steering shaft, etc. Just last week I got 17" Hummer H2 8-lug wheels and 285/70/17 BFG KO2s mounted on it, and Bilstein 5100s on all 4 corners, so now it's mostly ready for winter.

With all that said, it's pretty slow. The LQ4 makes what appears to be great oil pressure, and if left in gear it will rev to close to 6k no problem while making good LS noises, but yeah, slow, and yes I realize I was spoiled by the V. I'm also in CO at about 6,000' elevation, so I'd like to figure out what the best bang for the buck would be on this beast to give it some more ***** without breaking the bank during the house projects.

I had a PPI done on it before buying it, and at that time the shop let me know that they thought 3 exhaust header studs were broken which I understand is a common problem. The truck also has valve cover leaks (and some other oil leaks that I'm also looking at addressing) -

So with that in mind, I'm tempted to go a bit further than necessary in just resolving the exhaust issues (can smell fumes in the cabin at a stop when air is not in recirc) and do the following:

Order some Speed Engineering Long Tube Headers & Y-Pipe, and while we're in there, pull the heads and put better heads on it. I realize if I go square-port I'm also looking at a new intake, and if I upgrade to a newer throttle body I'll also need an X-Link and of course a tune afterward (I do already have HPT Pro with credits.)

If I go that far I imagine a cam also makes sense...

What would you guys do? The LQ4 runs strong but both it and the 4L80e are at 204k miles. I'd probably like to keep my parts spend less than $2k overall - figuring $~400 for the headers/y-pipe, ~$400-800?
for better (used) heads? ~$100 for a gen IV truck intake if needed + $250 for an X-link, and ~$200-400 for a cam? Would hopefully find heads with upgraded springs/trunions/etc if I look around.

Thanks in advance for the advice and input! I love sleepers so even getting this beast over 400 crank hp would help it not be a total dog.

FFDP

iTrader: (2)

If you enjoy the low end grunt and torque maybe keep the stock manifolds and do a camshaft upgrade still. Your 317's are great cylinder heads, no real need to get rid of them. A cheaper solution would be to just mill the heads to bump compression and gain horsepower/torque.

Do the intake manifold upgrade too and boom you have a great performing 6.0 with more horsepower/torque than factory and it'll stay quite.

You have many options that's for sure.

Tremek

Yeah I definitely like low-end grunt; having the V and an E55 AMG before that both with positive displacement superchargers ruined my butt dyno.

Are you saying just pull the heads, have them milled (and the broken studs extracted probably at the same time ) but keep the stock iron manifolds while doing a cam with higher lift? I have read in a couple places that BTR does a stock-valvetrain cam for Gen III motors but I haven't really investigated that route since I didn't feel good about trying to put more lift on springs with over 200k miles on them already...

Ideally I'd love to find a Magnuson supercharger for the beast and do a tune and cam at the same time and call it good, because who cares if the compression is relatively low with PD boost? But I'm not sure that's doable even with a budget-bump to $2500...

FFDP

iTrader: (2)

Yup, pretty much. It's just another option if you were keeping a tight budget and didn't have a for sure need for headers.

The bolts could be extracted and the heads milled at the same time for sure. They make low lift cams too if you didn't want a high lift cam. Something in the 212/218 range or similar so you didn't need a stall converter. Then new springs, lifters and pushrods to round it out. I'd replace the springs no matter what if you did a cam swap.

Joejamesatou

I have a 2005 3/4 Suburban as well. Had it dyno'd last week and it put down 260 HP at 5100 RPM. It is in the shop now getting the following:

Brian Tooley Stage 3 Truck Cam. Specs are 218/224 .553/.553 113+3.
LS6 valve springs
New pushrods
Speed Engineering 1-7/8 inch headers
Dual 3" Magnaflow exhaust with manual cutouts and X pipe
E fans with 160 thermostat to replace the stock clutch fan
Powerbond Underdrive Pulley
Tune by AMP Performance

I'll let you know the results.

big-joe

Let us know the results^^^^^

Best bang for the buck is gonna be a tune. Can pick up a lot on the lq4. If you have to mess with the manifolds already, headers would give a bit more. Gears help a bunch too.

Tremek

Joejamesatou: Also very interested to hear how that turns out for you!

Can you give more details on which pushrods you selected? I assume you're keeping 317 heads but adding the LS6 valvesprings? Where is AMP performance?

Fullpower

"What would you guys do?"

Re-gear it.
4.56 gears and a good limited slip diff.. I have been getting great service from the Yukon Dura-Grip.
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Adjust your Power Enrichment, the 6.0 were tuned very lazy, PE doesn't cut in until 90% throttle, and even then it is delayed, and about twice as rich as you want. LOTS of improvements are possible with the PE.

Tremek

My Sub 2500 already has 4:10s and a LSD due to its tow package, and spins at 2800? rpm at like 75 mph on nearly 33" tires; 4.56s are way too short for the truck to be usable on the highway.

I'm sure a tune helps, but I'm also at 6,000 feet above sea level and already down ~20% NA sea level HP and am trying to weigh how much compression I can aim for in the combustion chamber without having to rev the truck to 6k each time I want to get out of the hole, and while staying away from forced induction for the time being since everyone seems very skeptical about towing longevity if I want to put something heavy behind the truck for long distances. Tough decisions!

At this point I'm leaning towards headers, new heads that can bump the compression ratio + better valve springs while we're in there and better pushrods, e fans, a mild-to-mid cam, and a tune, and otherwise just leave the throttle body and intake alone. I really don't want to make a huge sacrifice in torque to get a bunch of HP when the truck lives 95% of its lift below 3500 rpm.

Fullpower

If you don't want to 'SPIN' it, then you'll need manifold pressure to make power.
CHEAP turbo is the way.
Stay under 10PSI manifold pressure, you should be able to get long engine life, good fuel economy, and still lay serious waste to your tires in the lower 2 or 3 gears anytime you want.
Really, if you won't regear for optimum efficiency, turbo charging is your cheapest route to performance.
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. edit to add:
Your camshaft plans are counterproductive, 6000 feet, heavy vehicle, TALL gears and 33 inch tires: recipe for even more gutless.
Save your money, you do not need cams, tubular headers, or any of that piece-meal micro-upgrades... leave the engine stone stock, and turbocharge it.
stock 6.0, stock heads, stock gears... put 10PSI in the stock manifold, you'll push 500 horsepower through stock muffler, smooth, quiet, your wife won't hate it, and it will tow anything your transmission can handle..
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I see you are in Colorado. Rolled through your state 6th of September in 3.5 hours. Wife drove straight through, I mostly slept in back.