Hey guys, I picked up this really clean 03' 2500 with 75,000 miles a few weeks ago. 1 owner truck, in excellent shape. You'll have to ignore the garish looking dual exhaust in the photo. I had both of the tail pipes cut off, a stock used muffler put on with a dump right at the axle.

The truck is stock otherwise and I decided to put it on the dyno to see how she do:

242 whp and 293 torque.

This seemed low to me, but the shop owner told me his dyno is 1 year old, calibrated and he puts it on the no bullshit numbers setting which is SAE and smoothing factor 5.

Truck has been compression tested and looked good across the board. There was a slight manifold leak (common) which I had addressed.

This truck has 3.73's and is rated to pull 9,900lbs and I plan to basically max that out with regular towing duty. My 5th wheel comes in at 9200lbs. So I had it tuned on the dyno.

Completely stock, tune only on 87 Octane it came up with 257hp and 311 torque (+15hp and 18ft-lbs of torque). The shop owner said he could tune more but on 87 octane and working it hard with the size of my trailer that pushing the tuning limits of the tune for a handful of extra horsepower and torque wasn't worth it. The torque gained under the curve was as much as 23ft' lbs in a few place.

Overall the truck feels stronger now and I look forward to working the **** out of this thing! I just ordered a K&N drop in on Amazon but I don't plan to do anything else unless she can't pull how I want her to.

 

Nice.

For a 6.0 and 4l80e otherwise stock, that is about right.

Look at the heads, you more then likely have the 317s which are ok but you would pick up more torque everywhere if you swapped out to the 706s.

 

I woulda ran 89 octane if available. For the extra 2-3 bucks per tank you have more peace of mind for keeping knock at bay and might have squeezed a few more horsepower from it.

 

Those numbers look pretty good for a stock set up considering the drivetrain loss of the 4l80,4x4 and larger rear. I am getting my pretty much stock 06 1500HD tuned next week so i'll compare numbers with you then.

 

More timing will net more power. The power enrichment delay removal is usually 15 hp on it's own on those hoopty's as Gm decided it intelligent to try to have the truck stay at stoich for an entire minute when you go WOT. If a 1500HD has 3.73 the truck is rated to tow 7900 lbs and 9900 lbs is for the 4.10 gear trucks. Its right in your owners manual. From the pic it's actually 8200 lbs as 1500hds were all crew cab trucks making your extended cab a light duty 2500.. which is the same truck anyway lol.

I suggest adding a GMT900 airbox ( at least the lower portion of the box itself) and cutting the fender to match. When you pull the air filter out take a look at how tiny the holes are that it is supposed to breathe through. I spin my trucks LQ4's to 6000 rpm and it was a noticeable change across the band on the MAF after changing the air box and cutting the inner fender.

For reference I have run up to 27 degrees of advance wide open on LQ4's on 87 fuel and gotten no knock. The only variance is my 05 1500HD which I wouldn't be surprised has an LQ9 in it and not an LQ4 as it's always had more power and always been octane sensitive than any other LQ4 I have had.

 

My results over the weekend after a tune were 276hp/311tq so I would say your numbers are about right my truck is stock except a kn drop in filter airiad tube and a borla muffler. I have 4:10 gears and running a 286/75/16 tire which didn't help i'm sure but it does feel a lot better now. Longtubes and efans will be next for me maybe a tbss intake later if I can get over 300rwhp before touching any internals i'd be happy.

 

The results from your trucks are about right in my experience. My 2wd Express van with what amounts to a 320-330 HP 350 Vortec engine made 257 RWHP and 310 RWTQ through a 4L85E in 2nd gear and a 3.73 geared 10.5" 14-bolt on 93 octane. On E85 it made 272 RWHP and 330 RWTQ.. The engine at the time was a L31 350 with the GM 300 HP Marine cam, 906 heads that were cut for 2.02/1.60s to save the valve seats and milled .020" with a thin .016" compressed head gasket. Marine intake manifold and Doug Throley tri-y headers into the factory 3" dual exhaust piping, thunderbolt 3" cats, with a walker dynomax bus muffler and 4" tailpipe. I was on LT265/70R16s at the time with aftermarket 90s aluminum wheels.

 

For the record I discovered on a STOCK LQ4 I was tuning that the difference between 25 and 27* of timing is like 2-3 ft/lbs. I tend to stick with no more than 26* of timing with the stock cam. I set the total timing from 2,400-5,000 rpm to 24* and then climb to 26* at 5,200+. With a higher stall converter I tend to use 12* as the lowest value in the timing table as well. Really helps spool the engine against the converter when you snap the throttle open. With a stock torque converter you can still make the timing values higher at lower rpm just have to watch out for tip-in knock retard in hot weather.

When you start playing with cams I have run as much as 30* timing to reach peak power on my friends low compression LQ4. He had a big thumpy cam (230/235 .609"/.610" 114+4) and .080" thick cometic head gaskets as it was built to be a turbo engine. He has since gone back into the engine and added a set of milled and ported 241s, LS9 head gaskets, long tubes and a TBSS intake with a 90mm TB. Currently runs 25* at the highest value at WOT and 20* is the lowest value in the timing table. I have the timing all in by 2,400 rpm. The converter stalls about 2,500 rpm and the truck just comes alive from there and pulls hard up to 6,700 shift points. Last dyno was 357 RWHP and about 315 RWTQ though a 4L80E (2nd gear pull, unlocked converter) and GM 8.5" 10-bolt. The wideband on the dyno was showing right at 12:1 at WOT. I know the tune is a little rich but that truck has never had a wideband on it and never been dyno tuned except when it was on the dyno for 3 power pulls.

 

Just added efans and airaids new cold air intake with the dry flow filter, bottom scoop and larger tube for the fans. Used the stock 05+ harness and fans overall pretty happy with throttle response and know it's breathing better than with the stock air box. Always seem to get the mod bug after the base tune/dyno.

 

*statement retracted due to being dumb & misinformed*
either way, you're right on the 3.73s carrying a lighter tow rating than the 4.10s, though.