Exhaust Setup

adamstokes88 · November 16, 2009

I have a 2004 GMC Sierra 2500 SCLB 6.0 with 4:10 gears. Right now I have a Magnaflow 14 inch 2-1 muffler. It's a 3.0" inlet 3.0" out with 3.0" piping all the way back and a 4" tip. I will be getting a Blackbear tune but I want to get my mods finished first. When I install my headers with 3.0" piping all the way back will I get more flow running a dual in dual out muffler or should I stick with my current setup? Thanks for any input.

davzog · November 16, 2009

I initially had a Flowmaster with twin 2.5" tailpipes....just that change killed a lot of low end torque. Not good for towing...ugh.

So, I swapped the muffler for the longer Magnaflow (sounds more mellow and throaty) and changed the tailpipes to 2 1/4" on the recommendation of the muffler guy who is pretty smart in this things....

Anyway, I was amazed at the gain in low end grunt, and picked up about 1+ mpg....

The exhaust manifolds on the 6.0's are nicely formed and many folks say that headers are just a waste, as they won't do much better than the sotck manifolds.....I guess that might change if a person went with long tubes and re-did the exhaust....I dunno.

The 6.0 appears to need at least some back pressure to perfrom well, especially towing.

adamstokes88 · November 17, 2009

I just towed a 7200 lb. camper today for the first time since I had my exhaust put on. My torque is nonexistent, the truck would immediately start to slow down if I backed off the accellerator just a little. Is it the 22" magnaflow you went with because I definetely want my torque back. Thanks for the input.

ss502gmc · November 17, 2009

I just towed a 7200 lb. camper today for the first time since I had my exhaust put on. My torque is nonexistent, the truck would immediately start to slow down if I backed off the accellerator just a little. Is it the 22" magnaflow you went with because I definetely want my torque back. Thanks for the input.

I am curious about this also, I just got my manifold gaskets replaced and got a leaking oem muffler so a few people recommended the 22" magnaflow dual in dual out. I have an 8.1L instead of the 6.0 but after reading these it makes me 2nd guess on what to get! Im not trying to gain hp cuz its got plenty although more cant hurt!! i just want it to sound good but i def dont want to lose any power! But its always seemed to me that the motor needs to breathe more.

grandjonson · November 17, 2009

a good exhaust setup can be broken down into a few easy steps.the basic idea is to make the run as short as possible,make as few turns as possible,pull in fresh, cool air from the bottom,exhaust hot, used air from the top.

davzog · November 18, 2009

Engines apparently need a certain amount of back pressure to create low end torque...

My son has an 04 8.1L and switched to a short magnaflo and dual 2.5" tailpipes....he immediately complained about a loss of low end. He took it to the same guy who did my exhaust and went back to a single 3" tailpipe...most of the torque came back and he thinks it is better than with the stock muffler....

adamstokes88 · November 18, 2009

Thanks Hd classic 07,

I've decided to cut my losses and go to another shop to have a 22' welded in.

Thanks for the input.

davzog · November 19, 2009

Certainly...good luck and let us know the results....

mikevmax · November 19, 2009

Hd Classic 07 How does you truck sound inside the cab? Thanks

Prokopchuk_9 · November 19, 2009

http://www.magnaflow.com/02product/shopexd...all&id=5753

thats the one i run on my truck, i never lost no low end torque. i gained something if anything. its the 22''. i love it personally...sounds really throaty. kinda got some drone on the highway tho but its not that bad...

davzog · November 20, 2009

Hd Classic 07 How does you truck sound inside the cab? Thanks

I can hear a nice mellow sound.....no drone at any rpm, driving or towing. It is louded than wifey likes, but music to me....she complains about a stock exhaust...not rackety or nasty....I like it.

It is not real loud, and my son has the shorted Magnaflow on his 8 Liter....wish I had that one....ha

mikevmax · November 20, 2009

Thanks for the help.

adamstokes88 · November 21, 2009

Just got a 22" Dual in Single out Magnaflow welded in and got all my torque back. Now i'm getting 100 miles to the 1/4 of a tank again. Seems to do better than stock, i'll see when I tow the camper tommorrow.

davzog · November 21, 2009

Just got a 22" Dual in Single out Magnaflow welded in and got all my torque back. Now i'm getting 100 miles to the 1/4 of a tank again. Seems to do better than stock, i'll see when I tow the camper tommorrow.

Let us know...I am certain you will be happy!!!!!!!!!!!!!