HELLO ALL-

I have a 2003 2500HD crew 4x4 w/4.10 gears with HPP3 set on 93 octane and 5600 rpm shifts,K/N filter,MAFS screen removed,265's- NOW what I would like to know is what replacement muffler is the best that would still be quiet and give me some low end hp/tq (for towing my 27' snowmobile trailer) and is the 180 deg thermostat worth installing??

BTW- is the K/N filpk(?) kit worth it? or any others?

THANKS-BJ

 

Is your HD a crew cab? I can only comment on the crew cab that you will have a hard time finding a setup that is acceptable drone wise. Something about the crew cab volume and the 6.0.....

I understand that magnaflow is the muffler of choice for most on this board.

Mike

 

You need the dual in/out muffler that Flowmaster carries for our trucks. Also on the intake. I reccomend the UPD. I had the FIPK switched to the UPD and felt a difference. The T-stat isnt worth it unless your getting detonation under acceleration.

 

Thanks Mike and 1badhd-

1badhd- if I change the program on my HPP3 to the "thermostat installed" option- does the computer give me more timing? and who is UPD for the air intake- not familiar with the brand-BJ

 

here is UPD's link http://www.ultimatepd.com/ they are a sponser that is located to the right -> i have a custom built intake with a afe conical filter on my 5.3 and i think that is fine. plus it cost a whole lot less than the after market prices.

 

Big John

I have a K2500 Yukon XL with the LQ4 Vortec 6000 similar to your truck. It too has the 4.10 axel ratio and I have the 4L80E transmission. I am an engineer and a former Detroit Diesel truck mechanic. I use my truck as my daily driver and to occasionally tow my 8,600 pound 1991 Airstream Trailer. I have tried to modify my truck with the following goals in mind: more torque and more efficiency. I want the power when I want/need it, but otherwise I want to preserve the efficiency when I drive conservatively. I still use 87 Octane.

Mods that I would recommend (in order of importance):

1. Install a bigger (higher lift/duration with some advance ground into the cam). I installed the Comp Cams 54-412-11 cam with 915 springs and 774 retainers. This is a relatively mild cam that really woke up the engine. I have the Hypertech III set for 87 Octane and the shift points are at 5,800 RPM's with a Rev Limit of 6,000. I am running stock lifters and push rods. For more details on the cam, see https://ls1tech.com/forums/showpost....2&postcount=48.

2. Add long tube headers for low to mid-range torque. I haven't done this yet, because I'm waiting for Thorley to market the 312Y Tri-Y headers due out early in 2004. Four into one long tube headers like The Other Guys (TOG's) or Arizona Speed and Marine (ASM) will benefit your bottom end torque a little more and limit your power above about 4,500 RPM's somewhat. The Tri-Y design benefits a broader RPM range but probably does not do quite as much at low end as the long tubes but they continue to enhance power in the upper register where a bigger cam will really shine on a small block. Personally, I'm sold on the Tri-Y concept. If I had a 4.8 or 5.3 engine, I would have installed their 310Y headers as soon as they came out. Be sure to get Ceramic Coating whatever you buy. The ceramic coating retains the heat inside the tubes (which enhances gas flow) and excludes heat from the engine compartment which is a plus for everything else in the engine compartment.

Speaking of cats, “there’s more than one way to skin a cat.” This has been my approach and I’m pleased.

Regarding a Cat-Back exhaust system, I don’t think that you will gain a thing except a different exhaust sound and possibly some really obnoxious noise. Take a good look at the factory exhaust system that came on your truck. It’s really low restriction. In fact, compare your exhaust system to that of the 8.1 Liter installation in the 2500 HD trucks and you will see that it is virtually the same. You have two big diameter cats. Dual 2.8 to 3 inch exhausts flowing through a huge dual inlet/dual outlet muffler. You won’t do much better here.

3. Improve the air induction system. A good aftermarket filter design using plastic ducting designed to minimize restrictions will work best. I have installed the Volant system (without the ram air scoop) and it works great and is quiet like the factory system except at and above half throttle where is sounds authoritative but not obtrusive. The chamber on the Volant tube and the factory tube is a resonator chamber. This does no harm to the air flow but it is designed (like an exhaust resonator) to absorb and dissipate sounds of certain frequencies. Also there are free mods you can do like cutting off the portion of the EGR tube that projects down into the air stream just after the throttle body and porting the throttle body itself will help somewhat. Do some Google web searches; there are lots of good resources telling you how to do this. GM High Performance magazine just featured a free mods article recently on an F body with an LS1 engine. Note: I don't like the mod to remove the screen from the mass air flow sensor because the screen does two beneficial things. First it diffuses the airflow so as to balance the air flow above and below the centerline of the MAF sensors and thus helps to improve the accuracy of the MAF data to the powertrain control module (PCM). Secondly, it serves as a back up filter in the unlikely circumstance that your air filter came off, developed a hole, etc. The MAF will flow plenty of air with the screen and the tiny power gain in the upper RPM register would be virtually imperceptible.

 

Thanks hawk-

Steve- I dont wish to change cams- and I think I have some info for you- the 8.1 muffler and 6.0 muffler look identical BUT the 6.0 has some major diff. internally that actually shut down one of the inlet tubes vs the 8.1 muffler is wide open (in comparrison), a good friend is a muffler dude and he cut each one open to see the difference.

My personal experience and recomendation from TPIS- I could go from "barely" doing a burnout to "easily" spinning the tires by removing the screen, and if you take the screen and compress it you would see roughly 25% restriction due to the screen itself.

I will look into the Volant system (thats what TPIS uses on there mod vettes) and people are recomending the Magnaflow muffler.

I doo appreciate the info but look into what I mentioned- you will be pleasantly surprised-BJ

 

Big John,

Thanks, I'll check both out. I could take the screen out and check it out and reinstall it if I wanted to. I'm open minded about the muffler too. I think that Gipson may have a pretty good direct replacement muffler too as I recall.