Flowmaster Mufflers

chevyHDjav · May 8, 2003

Has anyone installed Flowmater Mufflers on their trucks? I have a 2003 silverado HD with the 6.0 engine. Can you notice a difference in performance versus the stock muffler?

BadBowtie · May 8, 2003

I have heard a few with Magnaflows, and they sound awesome, they are supposed to be better for performance than flowmaster. Also take a look at the Dynomax Ultra-Flo

-John

Professor · May 8, 2003

I installed a Flowmaster Catback on my 99 2500 6.0. It killed the low end torque. It pulled a bit harder in the 4000 to 5000 range, but was worse everywhere else. I put a stock muffler and tailpipe from a 8.1 back on it. This restored the low end. I verified the results with my G-tech. IMO the reduction in backpressure is the problem. With a different camshaft profile AND ecm tuning, the flowmaster would be a better choice. GM engineers did their homework tuning to the muffler.

cowboy02 · May 8, 2003

I've heard good things about magnaflow also.

I think all in all try to find audio clips to check out the sounds and then Performance wise they are all close to a wash. Unless you do something drastic like headers and manrel bent tubes I don't see how you can get a gain. IMHO.

WEFs99 · May 8, 2003

I've got Flowmaster and maybe that's why my truck is so wimpy at low end.

1BADHD · May 8, 2003

I had true duals on my 2001 HD for over a year. Just this Monday I went with the new Flowmaster muffler that has dual 2.75" inlets and dual 2.5" outlets. I dumped the exhaust right behind the axle with 3" tubing. Now let me tell you, its like a different truck. I gained back all my lost low end. I guess since both pipes go into one muffler the back pressure is restored. But, yet still free flowing due to the 3" mandrel bent dumps. I reccomend this muffler to ALL HD owners. :thumb:

BDBWTE · May 8, 2003

I bounced back and forth many times between straights, stock, glasspacks, straights with one pipe, dual flowmaster 40 series and then to the Flowmaster big block 50 series that 1BADHD described and for what it's worth its the best muffler all around. Still have your low-end grunt but it opens up your top end too. Do not put 40 series on your truck I had them they sound good but de nut your truck the same as straights. Trust me I've probably have more $$$ in exhuast on this one truck than anybody has one one vehicle alone.. You figure 150.00 or 200.00 a pop for labor and pipe then tips and muffler were my dime.. I'd go with the BB 50 series, but that's my $0.02

tps0424 · May 9, 2003

I've got dual 40's on mine. They are 3" in and come out into 2.5" pipes that run up and over the axle and then into 3" stainless tailpipes. It was a custom job. I definitely feel more power all across the board with this setup. Maybe it's the 2.5" that allows me to keep the backpressure. All I know is it sounds great and I gained, not lost, low end grunt.

Stomper · May 9, 2003

I have a 2003 1500HD 6.0L. I had custom duals put on at a local muffer shop. Dual 40 Series Original Flowmasters, 2.75 in and 2.5 out. Man does this setup sound good. I only have 1200 miles on the truck, but just by the seat of the pants test I can't tell of any power loss.

If you want a good sound go with the 40 Series Flowmasters.

NSRacer · May 9, 2003

1BADHD or BDBWTE: you guys have a part # for that particular muffler?

1BADHD · May 9, 2003

Flowmaster info

Part number I used is 527504.

timk49 · May 10, 2003

I have a 2003 2500 HD I installed the Flowmaster that was recommended to me by the guy who owns a local muffler shop. He also owns a truck exactly like mine. I listened to his truck and he took me for a spin in it before I decided to buy the Flowmaster. I wanted a deeper truck sound without loss of low end and improved power towing up the steep grades. Thats when the tach nears the 4000rpm zone.

It's part number 530513 dual in single out. The muffler comes with the pieces to fit right up to your stock configuration. $290.00 installed.

It sounds great, not to loud outside and doesn't sound to loud in the cab. Towing has been fine. I 'd recommend this one. Anybody know why another set up is better let me know.

BDBWTE · May 11, 2003

Flowmaster info

Part number I used is 527504.

Rodger that's my part number. I payed $100.00 for the muffler and installed it myself and welded it myself because these douches around here can't put a weld down without it looking like a thimble.

As far as the 40 series go unloaded the truck feels stronger but go hook to a gooseneck with 6 ton or so on it and try to back up a hill you'll feel your loss their I garuantee. If your not trying to pull your truck like it is a 1 ton dually diesel then you'll probably be fine. But those who don't have the $$$ to buy a 1 ton must make do with what we have thus I pull hard.

chevyHDjav · May 12, 2003

Thanks for all the info. :thumb:

Mortgage Paul · May 17, 2003

The new 8.1 muffler from what the local shop here said is tough to beat on the 8.1 and really shines on the 6.0.

I also read on the Kenne belle site that the 8.1 is as good as it gets, but if you want a deeper sound, but aftermarket, but theres no power to be gained, and maybe a loss of low end.

Id really like more sound(deeper not much louder) but am reluctant. Plus the stock 8.1 system is dual out to a 3.5 single outlet. Pretty good sized for stock.