Hey all, new to the forums and this will be my first post. I have a few questions and have tead up on many forums but none pertain to exactly what im looking for.
I have an 03 gmc 1500 with a 6inch lift and 35" tires and the truck has around 135,000 miles on the stock drivetrain and motor. I want to make this truck fast but dont know if its worth modding out the motor because of the mileage. plus I live in california and would still like this thing to be street legal as far as emissions goes. So im trying to build up a lifted truck with ls motor being able to put out as much power as possible. Any suggestions would be great. Thanks

 

Probably better to post on PerformanceTrucks.net. Truck-specific site. Your login should work over there as it's basically the truck section of this site(see the links allll the way at the top of this website).

That being said, as long as you have maintained it, 135K is just getting broken in for a good LS motor so mod away. Plenty of guys here putting heads and cam on LS1s with 150K+ miles.

With a lift and tires on a relatively heavy vehicle, your best bet to make your truck peppier is gears. Doesn't sound that exciting but this will make the single biggest difference in performance right now. Then get a basic tune and go from there. Gears and tune should at very least make the truck a lot more fun to drive.

Good luck with your truck.

 

Ok I will head over to that forum but thanks for your reply. But that being said would a supercharger or turbo kit kill the motor and drivetrain if stock before gearing. And gearing wise would you go 4:10?

 

If you kept it reasonable probably not. Turbos are all the craze(and very effective) but the supercharger would be more of a bolt on in a weekend kinda deal for you. Turbo is a bit more complex and must be designed very carefully to give you the low-end power that you need in such a heavy vehicle. A positive displacement supercharger(like a Magnusson(sp?)) would give you almost instant boost without a lot of hassle and is the way i would go on a heavy truck with big tires. 4.10 is probably a good place to start but look at a gearing calculator online like this one:

http://www.dragtimes.com/gear-ratio-...-mph-speed.php

That way you can put in your specs and figure out where you need to be.

 

I'd go with more gear, 4.10 gears are probably not enough. You first need to go with shorter gears to offset the taller than stock tire to at least get the ratio back to stock, then go even shorter then that to help turn the heavier rotating mass. Furthermore depending on the power-band of the cam used you might want even shorter gears. I'd figure on going with at least 4.56 gears.

 

Ill check that website out. Are there any good supercharger kits that are less pricey but still good. Like the weiand kits?

 

4.56 gear with 35" tires, would be like running the stock 245/75/16 tires(03 GMC 1500 4x4 truck) with 3.97 rear gears, and that's not even factoring in the heavier rotating mass of the 35" tires. That's why I recommend at least 4.56 gears. Furthermore as already stated the gear change will greatly help with off the acceleration, and hauling/towing. It also might even improve the MPG depending on the size of you stock gears currently in the truck. If you're even contemplating ever going with larger tires, like 37" then go with 4.88 gears.

 

Yea that makes sense I dont ever plan on going bigger I like the way it sits and rides now. Im just trying to get power out of it now I put an CAI, exhaust and programmer chip im not sure if I mentioned but that added a very slight amount of powe. I live in CA so im not sure how much cam work I can do and still pass smog thats why I was maybe looking at getting a supercharger or procharger. The thin is im not willing to spend 5 to 6k on a kit. Are there any other ways to drastically improve HP. Or any other prochargers that would work for this motor setup?

 

You can go with a cam that has at least -6* of overlap with a 5.7L and pass CA smog with a good tune, if you have a 5.3L you'll probably want more negative overlap, and with a 6.0L you likely could get by with less negative overlap. With the heads you can either go with cnc ported stock heads or get aftermarket heads that have a C.A.R.B. EO # like the AFR-210's and still pass smog, to include the visual under hood check. Increasing the SCR, and flow through the heads will do wonders even with a relatively small cam. I would also recommend a TC stall upgrade even with a stock or small performance truck cam(2400-2800 rpm).
BTW, what engine do you have..?

 

I have a 5.3l

 

4.56 gears find a supercharger with an EO# and call it good.
Big heavy trucks need torque, lots of it.
H/C can help but imo not worth the money spent in comparison to a SC $ to power.
Have the same truck (2wd) unless theres a power adder not sure its worth going H/C trying to pass smog and getting the gain SOTP youd hope for.
If you cam it keep on the smallish side.

Theres a truck in town similar to yours, pretty much stock but S/C it moves out real good.

 

Whats a good S/C I can slap,on it withought paying completely out the ***?

 

IMO, if you can swing the cost of a S/C kit for you truck application that has a CARB EO #, I say go for it! Otherwise go with a H/C/TC setup which should be well under $5,000-$6,000. For the Heads get either a set of TSP, PRC Stage 2.5 5.3L CNC Ported Heads, or have Advance Induction(AI) cnc port/mill you factory heads, and stick with a SCR around the 10.5 range. For a cam keep the intake duration(@.05") in the 208*-217* range, and the exhaust duration in the 212*- 224* range. The cam size you ultimately go with will depend on what rpm range you feel you need the most power increase at. You'll also want a good tune to maximize it potential.

 

Patience can find you a used Magnusson kit for $3K-ish. They aren't out there every day but I've seen them. More often than unicorns.

Positive displacement(the kind that replace the intake manifold, like the "Maggie" I mentioned) (not centrifugal that hang on the front of the motor) give you boost basically right off idle and that's what will make your truck feel FAST...like basically a 7.0L instead of a 5.3L. A Procharger or similar centrifugal supercharger will make impressive mid-high RPM power but you'll find yourself counting the seconds on your fingers at the light waiting on your boost to get in order. Need a big stall and a light car to make that fun IMO.

Agree with the others on 4.56+ gears if you want to be fast. Just run the calculator and figure out what MPH your shifts will be at and what RPM you will be running at highway cruising speeds in overdrive.. Then imagine yourself in the driver seat with shifts happening at those speeds and those RPMs(determines noise level) at cruise speed and figure out if that makes for an enjoyable driving experience.

It occurs to me that heads/cam/intake/exhaust/etc. would wake things up a bit and sound badass but since you have a relatively heavy vehicle and a relatively small motor, would make a lot of noise and only feel marginally faster and mostly only at high RPMs. It is still a way to go but the positive displacement supercharger will make you forget all about the money you spent the first time you hit the gas...and have the most streetable and fun power band. My last car was a 04 comp orange Cobra. Factory pos dis supercharger..and a bunch of other goodies. There is no describing the **** eating grin you get on your face when you're passing someone on the interstate at 70 in 3rd gear while smoking the tires. And then the look on their face when they see the smoke..and hear the whine of the blower!

In all fairness, overdriven Eatons are loud as **** in a really good, intimidating way, but you get the idea.

Good luck with your truck.

 

Ok thanks for all the feedback this has helped alot. It sounds like the easiest route is to re gear and get a supercharger. I have heard of people dropping ls2 or ls7 motors in these trucks as well. For the price would that be comparable? And be CA street legal?

 

Sorry I just read the last post. Where can I start looking for a used SC

 

Here on the classifieds or on similar sites..performancetrucks.net and others. You can post a "want to buy" ad too.

 

Do they make turbo kits for this truck that could still be CA legal? Or could I make one

 

Just found one. It is the STS turbo sytem whuch mounts underneath the truck bed into the exhaust. Does anyone know what this compared to a supercharger as far as performance and HP would be I cant find anything.

 

With turbo systems, just like superchargers, you can theoretically make as much boost and power as you want by upgrading components in the kit like the turbo or supercharger itself. A good target number for most kits is 30%-40% increase in power.

Still, the positive displacement blower will always make more power at low RPMs compared to other forced induction devices and is ideal for a heavy vehicle with big tires. Turbo would have the cool factor for sure but would make more of its power in upper RPMs. Boost would come in right above idle on the positive displacement supercharger and probably about 2000RPM on the turbo before you see anything meaningful and 3000RPM before it's really putting out a lot of boost. The way you deal with that is having a higher stall torque converter (and possibly even more gearing) to let the motor get into boost quicker. A bit like revving it to 2K-3K RPM before you pop the clutch in a stick vehicle.

Do you mud any? Would not be good for an undermounted turbo.