flowmaster or magnaflow

snorydermb · March 1, 2007

I have a 04 sierra 2500hd with a 6.0 and just wanted to know which sounded better and had the least amount of resonance in the cab Im going to have lou's custom exhaust change the muffler so what do you guys think

Bruce03Silverado · March 2, 2007

Magnaflow hands down!! I had one on my 03 1500. I drive my trucks a lot and am on the phone sometimes too and I couldn't have the resonance or drone. I had the Magnaflow catback with the single 4" out the passenger side in the stock location. I had the 22" muffler not the 18". The 18" muffler is a little louder but I went with the 22" and was glad I did. Chances are I'll be getting another Magnaflow on this new HD.

s-ten · March 2, 2007

I have a Flowmaster 70 series big block single in dual out on my truck and I like it. The muffler is not real loud, it's just audible at 65 MPH. Going about 40 MPH you can hear it when you get on the throttle a bit. I have a friend with basically the same set-up, same truck, same engine only with a Magnaflow muffler; it is a little louder all around but without any resonance around 40 MPH. I like the sound of both, the Magnaflow has a little more of a burbly sound to it.

soccermom · March 2, 2007

I had a magnaflow 12599 on my 6.0 and it resonated like crazy b/t 1500-1800 rpm. Sounded great WOT and at idle and was quiet cruising but the resonance killed me day to day. I ditched that for a flo-pro which was better but after about 25k started to resonate pretty badly. IMO stay stock and get a tune instead, the 6.0 is hard to 'upgrade' without resonance. FWIW, I guy I know has the same muffler on his 1500HD/6.0 but he has 3.73 gears. Sounds better than mine but still resonates in that general range, though I could have lived with that. Lous in Peabody did my work & did clean installs for reasonable $. If you want dual pipes I suggest buying mandrel magnaflow pipes online instead of using the aluminized that lous sells.

Ryan11405 · March 2, 2007

MAGNAFLOW!!! better gas mileage, not as loud as flowmaster. i just had it put on my truck. I'm satisfied!

dklumph · March 2, 2007

I have a 04 sierra 2500hd with a 6.0 and just wanted to know which sounded better and had the least amount of resonance in the cab Im going to have lou's custom exhaust change the muffler so what do you guys think

I personally cannot say that I've used either but I've pondered the same question recently and for now...decided to stay stock. I wanted something that 'purred' a little more than stock at idle and sounded great when you stepped on it but I didn't want to sacrifice in-cab sound for it. I originally was leaning magnaflow mainly because of reading the boards and seems to be a favorite among many. I visited Flowmaster's site and for our truck, the 6.0, I think their recommendation is the 50 Series Big Block. According to their site's chart it was the quietest muffler they make. I believe I had read posts somewhere either here or on fullsizechevy.com about that muffler even being too loud in-cab on the 6.0. I called flowmaster and the person I spoke to actually recommended against buying one of their mufflers for the 6.0. He said the 6.0 is inherently a loud engine and they've had a lot of complaints from customers after putting flowmasters on the 6.0 specifically. So...with that I decided to hold off on my muffler upgrade for now.

In cab with window up, I can still hear the stock muffler rumble just a little...definitely not the kind of sound you get from high-flow performance mufflers but I just can't risk making it to loud in the cab of the truck for my family on long hauls. I personally could probably deal with a little more in-cab noise but I know my wife would be whining about it on long trips....I know keeping the wife happy goes a long way to keeping me happy!

all of that said...I did find a local guy that does mufflers on the side. He recommended a dual muffler setup. He uses some kind of flowmaster knock-off and sets them up on end side by side. One pipe in/out of each. the outputs tie together with the standard Y pipe to single out stock setup. He did a 6.0 2500HD of a friend of mines and his truck sounds nice. At idle it's just barely over stock but definetly sounds nicer. Revving it sounded great w/o back firing/popping. I haven't ridden it to see how the in-cab is though. I guess for me...if I decide to go down this road I HAVE to ride in someone elses truck with a paticular exhaust so I can hear it first hand before I take the leap.

so...back to your question...I guess I'd definitely say flowmaster is out based on my preferences and what the flowmaster guy told me.

Sorry for the long reply.

Don

curly · March 2, 2007

Since we are on this discussion, has anyone got any dyno information after swapping the factory cat-back for a Magnaflow? I would like something a bit louder at idle but mainly I want the performance of a better flowing system. I'm not willing to give up a quite cab to resonance.

I had a Flowmaster Delta series (supposed to be quieter) on my '03 1500 and the interior noise was bad at cruising speed.

Jimmy J · March 2, 2007

...I called flowmaster and the person I spoke to actually recommended against buying one of their mufflers for the 6.0. He said the 6.0 is inherently a loud engine and they've had a lot of complaints from customers after putting flowmasters on the 6.0 specifically. So...with that I decided to hold off on my muffler upgrade for now.

... I personally could probably deal with a little more in-cab noise but I know my wife would be whining about it on long trips....I know keeping the wife happy goes a long way to keeping me happy!

so...back to your question...I guess I'd definitely say flowmaster is out based on my preferences and what the flowmaster guy told me.

Don

You must have talked to the same guy I talked to as well. He told me the exact same thing. 6.0L is one of the hardest motors to get the perfect exhaust note...i.e., nice throaty rumble without in cab resonance.

As for the rest of the quoted statements above, same goes for me. I'll be staying stock as well. Have to keep the wife happy. Sure I would love to have a truck that sounds like a TRUCK, but not at the expense of in cab drone.

And, for those who want performance gains, without a doubt you'd get better performance gains from a custom tune vs. a cat-back system or the like!

kdog55 · March 2, 2007

I don't understand what the big deal is about Flowmaster on here! I have that exact same Flowmaster (50 series BB) on my 6L Ext. cab and I was actually wanting MORE noise out of it. And I am no punk-a$$ kid either- actually a 37 yo father of 2! I would recommend the 50 series bigblock Flowmaster to anyone not wanting TOO much noise. Heck, mine even bolted on to the stock pipes without much effort at all. Dual in/dual out even!

One of my co-workers is going with the Flo-Pro next week. He will probably post on here about it then. I am sure he and I will compare notes and let you guys know what is up. Right, EK?

But as I said, I like the sound level and tone of my tuck, but it FAR from loud. I would say only slightly louder than stock witha nice throaty rumble. And I have zero in-cab resonance at any speeds. The only time I even know I have a Flowmaster on is when the windows are down and I dump it or if I downshift into L2 or L1 for some reason. And there are 2 other guys on this site that can attest to what I am saying. Don't be scared away from Flowmaster at all, unless obnoxiously loud is what you want!

jonaddis84 · March 2, 2007

Has anyone heard a Corsa in person. Listening to their sound clips for the 6.0 in the Denalis it sounds pretty filthy! (good haha) But Im sure the engines are a bit different, and exhaust setup might be different, but should sound relatively close to the same.

What is the muffler/pipe setup in the 2500hd's? Two in one out? One in one out? Sizes of in and out? Its all mandrel bent stainless right?

kdog55 · March 2, 2007

On my '05 Sierra 200 HD EC it is definetely dual in and dual out and then it "Y"s together into 1 tailpipe after the muffler. Without going out in my muddy driveway and crawling under it, I think mine are all 3 1/2" SS.

Jimmy J · March 2, 2007

kdog nailed it. 2 in 2 out into Y for a single out. I think they're 3.5 in & out.

dklumph · March 4, 2007

I don't understand what the big deal is about Flowmaster on here! I have that exact same Flowmaster (50 series BB) on my 6L Ext. cab and I was actually wanting MORE noise out of it. And I am no punk-a$$ kid either- actually a 37 yo father of 2! I would recommend the 50 series bigblock Flowmaster to anyone not wanting TOO much noise. Heck, mine even bolted on to the stock pipes without much effort at all. Dual in/dual out even!
One of my co-workers is going with the Flo-Pro next week. He will probably post on here about it then. I am sure he and I will compare notes and let you guys know what is up. Right, EK?

But as I said, I like the sound level and tone of my tuck, but it FAR from loud. I would say only slightly louder than stock witha nice throaty rumble. And I have zero in-cab resonance at any speeds. The only time I even know I have a Flowmaster on is when the windows are down and I dump it or if I downshift into L2 or L1 for some reason. And there are 2 other guys on this site that can attest to what I am saying. Don't be scared away from Flowmaster at all, unless obnoxiously loud is what you want!

KDogg, thanks for your input...I personally have not heard the Flowmaster 50 Series BB so I wasn't really knocking it. I was going on what the Flowmaster rep told me. When I saw the exhaust on their websites chart as the quietest, liked the description and loved the sound clip on their site...I was excited about getting one. Then I called them just to make sure before I had one put on and based on what I was told by Flowmaster I shyed away. I like what you are saying though. I'd love to hear one in person and judge for myself. I just didn't want to spend a few hundred bucks on a muffler then feel like I (or family) couldn't deal w/ it. Based on your post I'm going to keep the FM Series 50 BB in mind when I do decide to check out exhausts again. I just bought a billet grille and westin bull bar so my mods are going to be limited for awhile.

Did you bolt your muffler on yourself or take it to a shop? Is the 50 Series BB the same length as the stock muffler?

Don

kdog55 · March 4, 2007

Actually, both!

MY budy across the street has his own shop and I used his lifts and tools, but it was simple. All I did was cut my pipes with a sawz-all reciprocating saw about an inch from the muffler on both sides. This leaves the stock hangers on the pipes to be re-used. I pulled out the tailpipe section to assemble that to the Flowmaster muffler while it was on the floor. This is where it was a little bit tricky, because the small "Y" that GM puts in their tailpipe leaves little room to play with and the line up is close, but not perfect. I only had to move mine about a quarter of an on inch, so I just heated the tailpipe at the "Y" and spread it out just a smidgeon, and it fit perfect. Then I manuevered the tailpipe and muffler from the rear of the truck, up over the axle and then into place. One thing you need to watch is that there is ample room betwen the spare tire (assuming yours is still underneath the truck) and the pipeing. Be careful to allow room for travel, because if it too close it could eventually rub and start the spare on fire. I know that sounds like an obviuos point, but I didn't even recognize how close it was until my buddy pointed it out to me because I was too focused on the muffler itself and lineing everything up. I used clamps on mine due to fact that my buddy was not comfortable welding Stainless Steel, and also I don't think the Flows are SS, so it would have been SS to plain steel. Anyway, no problems 2 years later and it never had the glasspack-type blowout that makes some real loud after so long. If I had it to over again without financial restictions, I might have went with a true dual setup, but then you go from a $170 project to about $400 and that was not in my truck budget at the time. But I am happy with my results, without a doubt. As I said earlier, if anything, I was expecting/hopeing for more noise, so I don't understand what everyone is complaining about. But to each, his own I guess. As far as length, it was within an inch or two as I reused all the same hangers in their original spots. I know on my 200 1500 I installed 40 series flomasters and they were much smaller than stock because i had to install a 10 inch peice of pipe to compensate the difference. All in all, I probably did the job myself in about 2 hours, but if you get a few buddies it is even less.

Also remember that by this time next week my buddy will have that Flo Pro brand installed and the way he described it, it has about the same dimensions as the Flomaster. I am sure he will post on that since it seems to be a hot topic around here. I know he paid roughly the same as I did for my Flomaster, ~$150, so it is a good comparison.

BC2500HD · March 19, 2007

I have a 04 sierra 2500hd with a 6.0 and just wanted to know which sounded better and had the least amount of resonance in the cab Im going to have lou's custom exhaust change the muffler so what do you guys think

I phoned Flowmaster about a cat back for my truck. (2003 k2500hd EC/LB 6.0L) they told me the resonance would be too much and didn't recomend their own kit. They said the 6.0L's exhaust note coming from the manifolds was loud. I did some research and found that Magnaflow didn't make one for my truck. I assume because of the noise of the kit. They make one for the 8.1L, but not the 6.0L. I ended up buying a Flo-Pro big oval muffler, from completexhaust.com. It's a direct replacment muffler and is supposed to throaty but not raunchy. My 2 cents.