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Discussion Starter · #1 · (Edited)
I've been driving my '65 'vert a bit since the new engine (about 325hp) went in, trying to put some miles on the break-in oil so I can change it. I like the new additional power but I am not happy about the new additional sound. My mechanic, who's into muscle cars, thinks it sounds great and I'm sure a lot of you guys would agree. Let me explain. I am retitired so I don't go to work daily, but I drive my Mustang as often as I can. I use it for everything, it's my car. It's not a car that sits in the garage and gets drivern 20 minutes to the car show. On top of that I like to listen to mustc when I drive. There's a cd player in the glove box, a pair of speakers in the dash and a pair of Boston Acoustics bookshelf speakers on the floor behind the front seats. I want to hear the tunes when I drive, not the engine. It's a cruiser, not a show car or a racer. Now I know a lot of guys like their car "fast & loud". I want my Mustang to be more "fast & quiet". Not silent (I know it's a 56 year old car) just a lot quieter. Has anybody accomplished that in their 65/66? What mufflers did you use? I'm currently using turbo style mufflers and resonators at the back and at 2,000 rpm or higher it's too loud. Like I said, it's a driver, a cruiser, a car I live with, not just drive for 20 minutes once in a while. It's got plenty of power so I don't mind if I lose 5hp if it means I can hear my tunes. Can it be done? Can my Mustang be fast & quiet(er)?
 

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Convertibles can be tough. My go-to is the Dynomax Super Turbo, which has fiberglass packing to further dampen the sound. If something like that is too loud, you could try Walker Quiet Flow mufflers.
 

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There is a Cadillac muffler that is reported to be free-flowing but quiet at the same time. I have read about it on Mustang forums but I can't tell you a part number.
 

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1965 Mustang GT350 Convertible
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I want it to be as quiet as possible, knowing that it won't be like a new car.
I'm with you on the quiet sound. I too have a '65 'vert. It had flow masters when I bought it. Much too loud. Changed to turbo style. Still a little too loud, but I'll live with it for now. Don't want to put too much more money into it now.
 

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67 coupe, 69 Sportsroof, 86 hatchback
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Found it, Walker Quiet Flow 21856. Thanks!
I've had an eye out for a good flowing but quiet muffler with a 2.5" inlet and outlet for other purposes. I thought this might be it. But after seeing that the #21856 necks down internally to like 1 3/4" I will keep looking.
 

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I'm going to try to make my 65 as quiet as possible. There's a world of sounds coming from a car that can tell a driver about problems before they become real problems.
 

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building a whipple 427 right now and keeping 2.5in exhaust on it so it's not too loud. I have headers, x pipe and dynomax ultraflows. Not too loud and they have longer ones so more sound deadening material. If I want more power I'll add a smaller pulley or something else not larger louder exhaust.
 

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Stock GT dual’s with resonators and transverse muffler is what you need.
I have this behind my 331 in. 68 convertible. Nice rumble on start up, a nice growl with the hammer down and quiet at cruise.
Absolutely no drone!
Be very careful with your choice of ordinary duals they have a habit of drone.
 

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The Dynomax Superturbo is a really nice sounding muffler with enough sound for a classic growl but not extremely loud. Just about all other performance mufflers are louder. I guess since not all turbo mufflers are equal its hard to say, but I would think that any of them with resonators would be really mellow. The Walker Quietflow is really tame. Mustang Steve has them on his fastback with a 427. Those are the 21856 for 2.5 inch and it doesn't seem to adversely effect that car from what I've seen.
 

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I've had an eye out for a good flowing but quiet muffler with a 2.5" inlet and outlet for other purposes. I thought this might be it. But after seeing that the #21856 necks down internally to like 1 3/4" I will keep looking.
More like 1-5/8" Ben. I had a coil switch malfunction while driving and when it reconnected the built up gasses exploded which caused the Quietflows to fail. I cut them open and measured the internal tubes at 1-5/8". If you've got hp to spare, they are quiet.
 

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I've been driving my '65 'vert a bit since the new engine (about 325hp) went in, trying to put some miles on the break-in oil so I can change it. I like the new additional power but I am not happy about the new additional sound. My mechanic, who's into muscle cars, thinks it sounds great and I'm sure a lot of you guys would agree. Let me explain. I am retitired so I don't go to work daily, but I drive my Mustang as often as I can. I use it for everything, it's my car. It's not a car that sits in the garage and gets drivern 20 minutes to the car show. On top of that I like to listen to mustc when I drive. There's a cd player in the glove box, a pair of speakers in the dash and a pair of Boston Acoustics bookshelf speakers on the floor behind the front seats. I want to hear the tunes when I drive, not the engine. It's a cruiser, not a show car or a racer. Now I know a lot of guys like their car "fast & loud". I want my Mustang to be more "fast & quiet". Not silent (I know it's a 56 year old car) just a lot quieter. Has anybody accomplished that in their 65/66? What mufflers did you use? I'm currently using turbo style mufflers and resonators at the back and at 2,000 rpm or higher it's too loud. Like I said, it's a driver, a cruiser, a car I live with, not just drive for 20 minutes once in a while. It's got plenty of power so I don't mind if I lose 5hp if it means I can hear my tunes. Can it be done? Can my Mustang be fast & quiet(er)?
IMHO, go to a local muffler shop with old guy who still has an oxy-acetylene torch in the corner..... drop the muffler and hanve him hold up different mufflers until you find what's good for your ear....IMHO, I would highly suggest Allied (bron wrap) resonators (glasspacks)..... look for something in the 30" plus length which will easily fit under our cars and you'll be happy..............deep sound, a little rumble, no drone and they last a very long time....I typically get 15-18 years out of a set on all my vehicles.
 
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I tried various mufflers to get the right tone, not drone or raspy sound that younger restorers seem to enjoy. Three chamber Flow Masters are not too bad overall. I could go quieter with Tesla mufflers but they are hard to find.:rolleyes:.
 

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I've got a 68 convertible with a big block and 2.5" exhaust. Did a lot of research for quiet mufflers because as stated you don't want a lot of noise/drone in a convertible. Used the Dynomax mention above and IMO is perfect.
 

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67 Fastback T5 331 TCI Frt End, Canted 4 link rear susp
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I just replaced my Flowmaster 50 Series Delta Flow with the DynoMax Superturbos. It reduced overall noise and drone, however based on what you are looking for, they may be too loud for you.
 

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Stock GT dual’s with resonators and transverse muffler is what you need.
I have this behind my 331 in. 68 convertible. Nice rumble on start up, a nice growl with the hammer down and quiet at cruise.
Absolutely no drone!
Be very careful with your choice of ordinary duals they have a habit of drone.
I second this. Originally on my 69 i went with the Waldron's transvers system here 1967-70 Ford Mustang V8 Dual Exhaust w/Transverse Muffler and Resonators

I selected the imposter muffler which was supposed to be much louder than the others. Even then, as kechke said, it had a nice rumble at idle and when you're really on it, but cruising I couldn't hear it at all. Zero. I had a coupe but always drove with the windows down. No drone either, period. Not at any rpm. With the new motor I built for my 69 i went with american thunder exhaust kit because I wanted it more rowdy, but the transverse system is now going on my 70. I can't recommend it enough if you want quiet and guaranteed no drone. They list it for 67-70 cars but it should fit yours, I think those are just the years the dual transverse were installed by the factory.
 
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