MS wrote:

I’m very surprised the Quiet Flows aren’t quiet enough!

I can't hold a conversion it's so loud and the wife refuses to ride in it.  And the only place where I don't have sound deadener are the doors.

As I remember you have the 17" versions from a Cadillac.  So maybe that's the difference.  But when I was looking Walker's catalog I wasn't able to find anything longer than the 14" one for 2-1/4" pipe, so I swapped out my dynamaxx ones for these thinking they would be quieter.  Turns out they appear to be the same.  Comparing the sound at idle and at 2000 rps w/ a decibel meter confirmed.

Have been thinking about installing resonators upstream of the mufflers but I have an H-pipe so I'm not sure how much length I'd have for them.  
 

BobE wrote:

Some more details would help.  Where does your exhaust end? (is it under the car, or out the side before the rear wheels, or straight out the back, or out the back with turndown tips?)
Do you have any sound deadener in the interior?
Are you sure that you don’t have a leak in the exhaust system?
What were the dB readings you found?
 
I have BBK Full Length Headers, mufflers are Magnaflow SS, 2.5"/2.5", w/2.5” Exhaust pipe w/turndown tips out the back. 
I don’t find the exhaust noise inside to be annoyingly loud and am able to talk in a somewhat normal tone.  I did install sound deadener in the interior.  As I have a fastback, adding sound deadener behind the fold-down seat and in trunk area (which is not as isolated as a coupe) did cut down on both road and exhaust noise. 

Very sure I don't have any exhaust leaks.  The pipes exit the valence.  I have a FB as well and have a rear seat delete with sound deadener under it.  I have a mass-backed carpet, so no sound deadener under it.  The trunk has sound deadener over the gas tank and the areas on either side, and I've also made a carpeted platform that fits over everything back there.  I don't have any sound deadener inside the doors or the quarter panels though.  I don't have the decibel readings any more.

You're not going to like this, but headers make the car noisier. A set of good flow cast iron exhaust manifolds, with a transverse muffler, and resonators will make it as quiet as possible, and still give it a distinct muscle car sound. It will also hurt performance- you have to decide which is the most important. If you want more noise, install cutouts to selectively turn up the volume. Don't forget sound deadening the floor, wheel wells, roof, doors, etc. In my old age I don't like unnecessary noise either, especially on long drives.

Mach1Driver wrote:

You're not going to like this, but headers make the car noisier. A set of good flow cast iron exhaust manifolds, with a transverse muffler, and resonators will make it as quiet as possible, and still give it a distinct muscle car sound. It will also hurt performance- you have to decide which is the most important. If you want more noise, install cutouts to selectively turn up the volume. Don't forget sound deadening the floor, wheel wells, roof, doors, etc. In my old age I don't like unnecessary noise either, especially on long drives.

After all the work I did rerouting my SS headers so I could run GT40P heads (plugs in a slightly different position), I'm going to keep them.  I'll install some more sound deadening, but I'd really like the exhaust to be quieter as well.
 

jkordzi wrote:

BobE wrote:

Some more details would help.  Where does your exhaust end? (is it under the car, or out the side before the rear wheels, or straight out the back, or out the back with turndown tips?)
Do you have any sound deadener in the interior?
Are you sure that you don’t have a leak in the exhaust system?
What were the dB readings you found?
 
I have BBK Full Length Headers, mufflers are Magnaflow SS, 2.5"/2.5", w/2.5” Exhaust pipe w/turndown tips out the back. 
I don’t find the exhaust noise inside to be annoyingly loud and am able to talk in a somewhat normal tone.  I did install sound deadener in the interior.  As I have a fastback, adding sound deadener behind the fold-down seat and in trunk area (which is not as isolated as a coupe) did cut down on both road and exhaust noise. 

Very sure I don't have any exhaust leaks.  The pipes exit the valence.  I have a FB as well and have a rear seat delete with sound deadener under it.  I have a mass-backed carpet, so no sound deadener under it.  The trunk has sound deadener over the gas tank and the areas on either side, and I've also made a carpeted platform that fits over everything back there.  I don't have any sound deadener inside the doors or the quarter panels though.  I don't have the decibel readings any more.

Well, seems you've done even more with sound deadening then I have done.
One suggestion; as a test, you might to try putting turn-down exhaust tips (even just temporarily) to see if the exhaust noise being directed down towards the ground offers any change ... just a thought. 
 

jkordzi wrote:

MS wrote:

jkordzi wrote:

I can't hold a conversion it's so loud and the wife refuses to ride in it.  And the only place where I don't have sound deadener are the doors.

As I remember you have the 17" versions from a Cadillac.  So maybe that's the difference.  But when I was looking Walker's catalog I wasn't able to find anything longer than the 14" one for 2-1/4" pipe, so I swapped out my dynamaxx ones for these thinking they would be quieter.  Turns out they appear to be the same.  Comparing the sound at idle and at 2000 rps w/ a decibel meter confirmed.

You can have the resonators on my 66 if I ever get them taken off and replaced with 2-1/2" pipe. They are Gas Doctor 2-1/2" and have 3" (pretty sure not 3-1/2") OD  At least 12" long.

There is a picture of my exhaust system on the 64.5-73 Mustang Tech Help FB page

Have been thinking about installing resonators upstream of the mufflers but I have an H-pipe so I'm not sure how much length I'd have for them.  
 

I have resonators on my 66 in front of the mufflers. But Al’s 65 with 408 had same exhaust as mine without the resonators and it was still quiet and sounded better out the back. Steve Buzek has 2-1/2 like mine in his fastback.

I guess the conclusion is that the extra length in your mufflers is the difference.  I wasn't able to find anything longer in the Walker quiet series in 2-1/4".  I see there are some resonators that advertise they also quiet the sound in addition to addressing drone, so maybe I'll try a pair. 

 

Nos681 wrote:

jkordzi, is there a possibility of something rubbing against the body making it noisy?

I had a bolt on transmission trim piece that contacted the transmission and raised the sound level in the coupe.

I also found a loose fastener holding one of the muffler/exhaust mount to the floor under the rear seat.

Well, I suppose that's a possibility that something is allowing some part of the pipes to touch the floor, making the body a giant guitar soundbar.  I'm going to get the car up on ramps tomorrow to get for clearance for resonators and will check that as well.

6sally6 wrote:

Do you wear hearing aids ?!
1. Turn'em OFF...end of issue
2. Try the Tesla mufflers !?
3. Get a better sound system !?
4. Try some blue tooth ear buds (with white noise playing)
5. (My wife won't ride in mine either...how pleasant THAT IS !)
6. Maybe convert the exhaust system to 1 1/2". Big pipes=Big sound.
7. After the H-pipe replace the exhaust pipe(s) with bullet style glasspack mufflers run in series..
6sally6

Always helps to get an alternative viewpoint