What are the quietest performance mufflers available?

gnvair

G-Body Guru
Sep 1, 2018
961
93
Southern New Jersey near Philly
I took my Malibu to a car show that was 2 hours away yesterday. It was the longest drive I have taken it on since swapping the rear. I realized at 49 years old that noise and vibrations REALLY bother me. Car is a mild 350 4 speed with 3.31 rear ratio. Exhaust is small Heddman long tube headers, 2.5 inch exhaust with Ultra flow mufflers and stock type tail pipes. No catalytic converters. Cruising around 3,000 rpms is 70 mph and gets quite noisy even though the car still has all of its original sound deadening. The exhaust drone varies depending on the rpm.
I would like to reduce the noise level to a more acceptable level. I just started looking at mufflers last night. I think I am down to either the Walker Quietflow SS or the Dynomax super turbos. I know both are offered in longer lengths. To me, chambered mufflers like Flowmasters or straight through mufflers like the Ultra flows are not acceptable. My thinking is that a reverse flow would probably be the best choice. I have even thought about adding catalytic converters back into the equation as they seem to act like resonators in some instances. I am curious to hear some opinions from others of what they found acceptable
 

565bbchevy

Geezer
Aug 8, 2011
9,192
113
Michigan
You could also try an insert like those from Car Chemistry if your style muffler will fit it.
I have Dynatech Vortex cones on the exit of the 4.5" 2 chamber Flowmasters on my Monte with full exhaust and it helped tone it down without changing the sound.
 
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Bonnewagon

Geezer
Sep 18, 2009
8,836
113
Queens, NY
  • Agree
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Bonnewagon

Geezer
Sep 18, 2009
8,836
113
Queens, NY
I used the long one on my Bonnewagon in place of the stock cross-mounted behind the axle muffler. On the TA I used the short Turbo style. They fit better under the rear seat floorboards.
 

gnvair

G-Body Guru
Thread starter
Sep 1, 2018
961
93
Southern New Jersey near Philly
I ended up swapping my Dynomax Ultraflows for Walker Quiet Flows. It's amazing the difference. Still has a rumble at idle but is quiet inside and no droning. I need more seat time, but the 20 minutes I spent driving it today really left me impressed.
First is the Dynomax Ultra Flows

Second is the recently installed Walker Quiet Flows.
 
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scoti

Royal Smart Person
Supporting Member
Sep 5, 2019
1,642
113
Texas
I used the 3" version of this muffler on my dually. Very tame. The set-up is a 454 w/a towing cam; 1.75primary/3" collector full length GM car headers; dual 3" head tubes w/a 3" 'H' pipe; the 3" inlet/outlet mufflers; dual tail pipes come out of the mufflers @ 3" & reduce down to 2.5" & are routed all the way dumping @ the corner of the bed/bumper. Mine is fairly decent @ 2800-3krpm/70mph & def quieter @ idle/low rpm cruise speeds for sure.
 
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Oct 14, 2008
8,247
113
Melville,Saskatchewan
The Super Turbo's probably would have been adequate. I currently have them on my 70S, even the short version have almost stock noise levels. Did you notice any power loss vs the straight through mufflers?
 

gnvair

G-Body Guru
Thread starter
Sep 1, 2018
961
93
Southern New Jersey near Philly
The Super Turbo's probably would have been adequate. I currently have them on my 70S, even the short version have almost stock noise levels. Did you notice any power loss vs the straight through mufflers?
I have had the Super Turbos and they are still louder. I still have a pair of the Super Turbos. I can best describe them as being between the Ultraflows and the Quiet Flows. The Super Turbos still drone at cruising speeds. Here is a pic of all 3 together. If there is a power loss it mostly is not a lot.
 

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