2500HD 6.0L exhaust modifications

Red2500HD · December 11, 2003

I just came from my local exhaust dealer and he showed me what Chevy has been installing in the 6.0's. As you know, the exhaust consists of dual 3" pipes with dual cats entering the muffler which LOOKS like two-in and two-out, right? Look closer, you only have one-out as the other is only a resonator and does not actually exhaust out of the muffler. Also in the in side, the 3" pipes are reduced to 1 7/8" inside the muffler. He is proposing to junk the stock muffler and install two turbo-type mufflers leaving the stock 3 1/2" tail pipe. I want to keep the single tail pipe for $$ reasons. He has done this conversion to several 6.0's before and has dyno figures showing a 20-30HP gain. He chargers $180 for installing the two ss mufflers.

So, what do you all think, is this a good idea? Will if hurt my torque output? Is it worthwhile?

1BADHD · December 11, 2003

Nope, that was one of the best mods you can do for the 6.0! The stock exhasut is restrictive. Put duals on and dont look back. If your worried about low end run a single tailpipe. I have true duals and lost very little if any low end.

2001BLACKHD · December 11, 2003

Did the guy at the exhaust shop know if any of the conversions from the stock muffler lost any low end torque? What mufflers did he use? Is there much in-cab resonance? I like the idea of using the stock tailpipe. I have noticed that flowmaster offers a kit that replaces the stock muffler and tailpipe with the same style factory set-up. Would'nt want to change the stock exhaust at the expense of in-cab noise or loss of power. However, a meaner sound would be nice!

1BADHD · December 11, 2003

A flowmaster will resonate. A 50 series is a better choice. Only resosnates at certian rpms. I have heard and rode in a HD with Magnaflow mufflers and it sounded great!! If I re-do my exhaust again, it will be with magnaflows.

Red2500HD · December 11, 2003

Did the guy at the exhaust shop know if any of the conversions from the stock muffler lost any low end torque? What mufflers did he use?

No he didn't, and that what makes me suspicious....he only had HP numbers. I pull a 5th wheel camper in season, and would NOT want to lose any torque, and when pulling, I am not that concerned with mileage. I just want a little more towing power.

The mufflers he suggests are a generic, turbo muffler made of stainless steel. Am not sure of brand. He stated that the system would be somewhat more noisy, and I can live with that, but would not want it too loud. I know some of you guys dig the decibels, but that's not my style.

2001BLACKHD · December 11, 2003

1BADHD

Were the magnaflows installed using the stock tailpipe? Any idea which magnaflows? I'm not sure that I have ever heard magnafow muffler. Do they sound anything like a flowmaster? Thanks

1BADHD · December 11, 2003

They didnt use the stock tailpipe, but did have a single 4" outlet. I think they were the Magnaflow XL's. They dont sound like a Flow. They are more rumbly and deep. Dont have that tinny echo. Kinda hard to explain.

d2bnorman · December 11, 2003

I've been wrestling with this situation for some time now. My exhaust shop told me the 6.0 needs a certain amount of back presure to operate at peak efficiency at lower rpm. They recommended a dual in, single out SS Magnaflow, part # 14590 for this motor. I had it installed about 3 months back and loved it except for the resonance below 2000 rpm, especially under load. I called Flowmaster to ask about their series 50 muffler that was designed for the 6.0 & 8.1 engines only, and was informed by their tech support that they have pulled it from inventory since there have been too many complaints about it being too loud, and to check back next year sometime for something new. Back to my exhaust shop, the owner felt bad about my $189.00 Magnaflow not sounding the way I want, so we welded in two small 12" long resonators just ahead of the muffler, they look like small glasspacks. This toned it down slightly and took the edge off of the "droning" at low rpm, above 2000 rpm it is deep and throaty, but not tooo loud. Hope this helps.

QUIKAG · December 11, 2003

I replaced the stock muffler with a dual in-dual out Dynomax Ultraflow muffler, keeping the rest of the exhaust system stock and it was unbearably loud. The resonance was incredible, it vibrated the floorboard. It didn't sound good at all. I had them weld the stock muffler back on.

If the muffler shop is recommending two mufflers, that might be a better idea. Make sure it's not a straight-through muffler though because you might have similar problems to what I experienced.

Red2500HD · December 12, 2003

If the muffler shop is recommending two mufflers, that might be a better idea. Make sure it's not a straight-through muffler though because you might have similar problems to what I experienced

This is EXACTLY the problem I am trying to address....too much noise vs. enough back pressure to maintaine torque. The dealer recomended two "turbo" mufflers which are baffled, creating SOME back pressure. He refused to recomend straight-through mufflers for the above reason. He wants to hook the mufflers into the stick tail pipe which is 3 1/2"& stainless. I am not a kid any more, and don't want it too loud, and I can't afford to replace everything and start new.

I see a lot of controversy when it comes to exhaust systems. Some want it loud and louder no matter what. I just want to get some more power for towing. Others want it super quiet. There has to be a compromise somewhere. If anybody has a solution, not just something they use because it's cool, let me know.

Mike's 2500HD · December 12, 2003

I have dual 50 series Flowmasters...they added some performance but, I am seriously thinking about changing to Magnaflows. The Flow masters are just too loud and they don't seem to give me the deep sound that I would like to hear from a 6.0L. They are kinda hollow sounding and get quite annoying at certain rpms. I have heard the Magnaflows and the sound great.

tbyrne · December 12, 2003

20-30hp seems a little high for replacing the stock muffler. You see those numbers from long tube headers. Replacing the catback is usually good for about 10 maybe 12 horsepower. I just wrote about this in the last thread so you guys are going to think I'm a walking Corsa advertisement I used to like aftermarket exhausts that could be heard before the car/truck was even seen. Now I like systems that are fairly quiet but still produce results. The Corsa exhausts are like having two different systems at the same time. They are pretty mello with limited to no interior resonance. You can hear a slight deeper exhaust sound while cruising down the highway but it's not loud at all. When the gas pedal goes to the floor it's a while different story. The system comes to life and lets people your that your truck isn't stock. This pretty much gives you the best of both worlds. They've recently added alot of new systems to the GM line-up so must truck configurations are now covered.

B&B TriFlo also makes a nice system. They also don't have to much in the way of interior resonance but I'd say they are a little bit louder during normal driving. Not to loud for a daily driver though.

Tom

2002 8.1 Silverado HD - Comp Cam, TOGs headers, Volant induction, Direct Hits ignition, 8" lift 18" wheels/tires + more

2002 8.1 Suburban -Intercooled Whipple supercharger, TOGs headers, Volant induction, 22" wheels/tires + more - 407hp/558 ft-lb torque at the rear wheels.

www.tbyrnemotorsports.com

regcab02HD · December 13, 2003

I've got the 6.0 with 50 series flowmasters. The sound is bada$$. It's not too loud. Sometimes I wish it was a little louder. I have no resonence. That may be because I only have a regular cab. I also didn't notice an increase or decrease in power.

HDROCK · December 13, 2003

When I first got my 6.0 in 2001 the first thing I did was take it to the muffler shop and I had them cut all the stock pipe off just short of the two cats. From there I ran 2 2.5 inch pipes straight out the back into a 4 inch tips. Let me tell you this was one mean sounding Devil but, the cops did not like it as much as I did and I had to take it off. I decided just to put my stock exhaust back on. I can tell you that there is a difference on the interstate with the muffler. The back pressure provides considerable low end torque which I lost when I had the duals on. The true dual exhaust however seemed to run better at higher RPM's than the stock exhaust. One thing I will tell you for sure run the exhaust out the side I know a guy who has a 5th wheel camper and he took it on vacation and the noise from where the exhaust bounced off the camper from his straight pipes drove him crazy

duffy · December 15, 2003

I'm in pretty good with a guy that owns a muffler shop. We cut off the stock muffler off my 6.0 and put a 30" glass pack on each side with 2 1/4 pipe straight out the back with 4" echo chambers. It sounds great! It has that deep dualed out tone without the really loud pop. I was up and down the interstate this weekend and there was no resonance, and I couldn't feel any torque loss but it does seem to pull harder at the higher rpms.