To install a dual exhaust system in a '65-66 car that was single exhaust you'll need the following...

a. Exhaust system, of course.
b. You can use HiPo manifolds or "log" manifolds. Each has their own "H Pipe". If you use HiPo manifolds and have a manual transmission with a clutch equalizer bar you'll need to either modify your existing equalizer bar or get a "HiPo" equalizer bar.
c. You'll need a dual-exhaust-specific rear flex brake line, bracket, and vent bolt (or cut down your existing vent bolt). You'll need a short extention to your existing chassis hard line or a new chassis hard line.
d. You'll need hanger brackets for the mufflers, under the rear seat, and tailpipes. The floor reinforcements for the hanger brackets are recommended.

 

To install a dual exhaust system in a '65-66 car that was single exhaust you'll need the following...

Im only assuming it was single exhaust when manufactured, but it currently has a dual exhaust system in place. I’ll get photos once back home.

 

I have an Arvinode exhaust on my 1965 Mustang. At the time none of the hangers were available so I just gave my exhaust pipes to the local garage and they hung it for me. Used log manifolds and a standard zbar for the toploader. Also used trumpet tips. Its pretty quiet also the pipes are 2 inches in diameter. I believe I got my exhaust system from NPD.

 

I suppose I should add in more info: currently it has a C4, but eventually I will change to a T5. I am planning a hydraulic clutch, not the original bar type setup. As Woodchuck mentioned, these pipes are not original but what I have now and how it is hanging is anyone’s guess till I get photos.

As @69RR stated, one option is to get all the stuff, throw it at the shop, and say “here ya go.” I’ve been leaning towards this, I just have to know what parts to get.

 

First off, I removed my Arvinode exhaust because exceeded the 100dB SCCA limit. A healthy motor but still. I sold it to @Jeepers.1966 who seems to love it in his convertible. Maybe PM him and go for a ride before you commit. You are almost neighbors.

 

Arvinode is sweet stuff, but may be louder than you prefer if it is currently too loud. What is on it now?

 

...just my 2 cents

If you are planning to change to a T5, I'd wait until after you switch transmissions to change the entire exhaust. For now, I'd just swap your current mufflers for a pair of Turbo mufflers. These will quiet down your exhaust for little investment. Put the rest of that budget to the transmission project then return to the exhaust system.

...this is if your actual goal is to just reduce your current exhaust level

 

Here’s what I’m working with now, and of course it isn’t as loud as it sounds in real life.

 

Sounds like Flowmaster or similar. I'd probably also suggest doing what Rufus said and just get a pair of Dynomax Superturbo or Thrush Hush mufflers. That will be a mellow sound where you can still talk or listen to the radio inside the car.

But if you still go with Arvinode, definitely upload a video so we car hear the sweetness.

 

Just so you know… My car with an Arvinode exhaust.

 

Regardless of noise, that’s one flipping awesome video! So, one thing that video did show me, which seems like the other videos I’ve seen, is that it’s actually pretty quiet at “normal” RPM ranges and idle, which is very much where I’ll do most driving…wouldn’t mind much if it was loud when really opening it up getting on an onramp or something. Is that so, or loud even at low to normal ranges?

Maybe I do have the wrong impression of it, and, if so, I’m looking for a nice low rumble for idle and then some spirit higher up. If I could compare to anything…I like the 06-09 GT exhausts.

 

The Arvinode exhaust is deceivingly mellow at idle and low RPMs. Not really trying to talk you out of it but there is a dark side when you get on it or are at highway speeds.

 

Nothing past the collector matters. This isn't F1 and we aren't smart enough. Do what you want. But go 2.5" or stay unserious and waste money on dreams.

Has it ever occurred to anyone that 98% of exhausts on here sound like hot garbage? If you have a Flowmaster on a Vintage Mustang and think it sounds good, we are enemies. You've been warned.

Arvinode is a waste of money. It's not going to make you like your car. Balls will make you like your car.

End of story.

Sorry to sound harsh but we've all been trapped in the "Shelby did it, it was awesome in 1967." Myself included. There's more scientific methods to achieve specific sounds with these cars. This is as good a place as any...

Thought I’d compile a focused post for anyone chasing specific exhaust tones out of a 289-powered '65–'69 Mustang. There's a lot of noise out there—so here’s a high signal breakdown of muffler types, crossovers, and their actual results on a typical street 289 turning 6,000 rpm max (we’re not talking Boss 302 here).

This assumes long-tube headers (Tri-Y or equal-length), 2.25"–2.5" duals. Focus is tone, rasp, volume, and real-world comparisons.

A stockish 289 (say, 9.0:1, mild cam, 600cfm carb, 6k redline) is going to have:

Naturally crisp midtones

Fast revving bark, but thin at low rpm

Lacks big-block bass or lopey thump unless cammed up

MUFFLER CHARACTERISTICS ON A 289

1. Arvinode (factory HiPo dual resonator setup)

Tone: Raspy, metallic, sharp-edged

Volume: Moderate to high under load

Best For: Vintage correctness, raw 60s sports car tone

Real World: Think early GT350, but thinner than you'd expect today. Zero drone. Cold steel clang. Not modern-loud, but noticeable.

Notes: Straight-through design with resonators ahead of mufflers. No crossover. No boom. High-pitched snarl.


2. Glasspacks (Cherry Bombs, Thrush)

Tone: Hollow, barky, sharp, moderate rasp

Volume: High, but tolerable if long enough

Best For: Raw and rowdy retro tone, “I'm not here to make friends”

Real World: Late-60s dirt track. Crackles on decel. Will drone if pipes are too short. Use long ones if you want to tame the ear fatigue.

With H-pipe: Deeper, rounder

With X-pipe: Higher-pitched, more shriek

No crossover: Staccato firecracker bark. Each pulse isolated.


3. Chambered (Flowmaster 40/44/Delta, etc.)

Tone: Boxy, synthetic, mid-heavy thump with some rasp

Volume: Medium to loud, depending on series

Best For: “Muscle car” tone with tight compression of sound

Real World: More Camaro than Mustang. You get that NASCAR-style “crack” at throttle blips but with notable drone.

H-pipe: Adds burble and punch. Good for balance.

X-pipe: Kills the thump, adds rasp. Don’t recommend X with Flowmasters unless you like flat tone.


4. Turbo Mufflers (Walker DynoMax, 2- or 3-chamber)

Tone: Smooth, broad-band, slightly wooly

Volume: Moderate

Best For: Daily driver tone, quiet-ish with authority when opened up

Real World: Think late-70s Ford, early Fox bodies. Old school cruiser. Not aggressive, but won’t disappoint under load.

Crossover effect: Both H and X smooth things further. X makes it sound modern, H keeps the V8 character intact.


5. Bullets (Magnaflow, Dynomax Race, etc.)

Tone: Brutal, high-frequency screamers

Volume: Extremely loud, little to no sound dampening

Best For: Track cars, shock value

Real World: If you want to sound like a CMC car or 90s NASCAR, this is it. But it’ll be intolerable on the street unless you like bleeding ears.

X-pipe only: You must run an X with bullets or it just sounds like angry farm equipment.

X-pipe tone comparison: 90s NASCAR with open header X-pipe howl. Almost two-stroke at high rpm.


6. Spiral Flow (Jones, Aero, etc.)

Tone: Unique—airy, turbine-like whoosh with faint burble

Volume: Quieter than bullets, louder than turbos

Best For: Modern builds that want unique tone and flow

Real World: Mix between turbo and straight-through. No drone. Sounds “fast” at idle. High-rpm has a buzzsaw quality if the cam supports it.

Crossover effect: X makes it sound high-tech, H adds some thump back

CROSSOVER PIPES: SOUND & FUNCTION

No Crossover

Sound: Each bank fires independently = raw, unfiltered

Result: Max separation = staccato pulse. Can sound “broken” on some mufflers. Works great with glasspacks.

Used by: Early Shelby GTs, vintage Trans Am builds


H-pipe

Sound: Deepens tone, smooths pulses, retains muscle character

Result: Bassier tone, less raspy, better low-end torque

Used by: OEM-style duals, drag cars, most American V8s

On 289: Adds a low-mid punch that makes it feel bigger


X-pipe

Sound: High-pitched, exotic, blended pulses

Result: Revvier sound, more modern or “race car” note. Often mistaken for higher rpm than actual.

Used by: NASCAR, modern Mustangs, CMC cars

On 289: Perfect for glasspacks or bullets if chasing 90s NASCAR scream. Avoid with chambered mufflers.

Sound Like a '66 GT350R: Arvinode, no crossover, long tubes. That raw metallic rasp.

Sound Like a Dirt Track Car: Long glasspacks, no crossover, dumped before axle

Sound Like 90s NASCAR: Bullets + X-pipe, as long as your hearing lasts

Sound Like Your Neighbor’s ’78 F100: 2-chamber turbo mufflers + H

Sound Like You Hate Everyone at Cars and Coffee: Flowmaster 40s + no crossover, cammed up, axle dumps.

This isn't anecdotal. It is science. Engines and sounds are things. And we seek to master things.

Enjoy your 4d science experiment! But don't get caught up in feeding the capitalism beast when a local guy can build you the exhaust of your dreams with crap off Amazon and a Tombstone for $300 all in.

 

I’m looking for a nice low rumble for idle and then some spirit higher up.

I like the 2.5" WALKER # 17733 on my '66 convertible. It is mellow, but has a nice sound during acceleration. You can listen to clips on their website:
Super Turbo™ - Offset / Centered Muffler - P/N: 17733 - DynoMax® Performance Exhaust Super Turbo™ - Offset / Centered - P/N: 17733

If you have a Flowmaster on a Vintage Mustang and think it sounds good, we are enemies.

I hate the Flowmasters on my '65.

 

Well, we've always been friends.

 

My buddy and me!

 

I would consider an Arvinode system for the wife's 65 under construction. I scored some new repo k code manifolds and an H pipe last year off Facebook for her car. I think the arvinode stuff would stay on it til the first time she gives it gas! Then I would have to take them off and put them on my car lol.... It's a budget manipulation thing I have a JBA shorty GT system on the 66 and the mufflers are LOUD, great throaty sound at idle, you are not talking on the phone or listening to the radio while cruising though. I like the JBA system, but like I said, its loud, maybe a little to loud.....I would love to try that Arvinode system on my car. I say go for it.

 

I would say go for it. I don't pretend to understand what jdub's motivations are for trashing several exhaust setups. Including the Arvinode I have on my car saying I'm wasting my money. I wager he and everyone else is "wasting their money on silly hobbies"..just talked to a friend who just got a 38 ft sailing yacht..is he wasting his money? Probably but am I going to tell him? No.
Everyone has right to their opinion but opinions are like ass*oles everyone has one. Unless you put exhaust systems on for a living then I value your opinion as much as value my mom's opinion on exhaust sounds. Actually I value my mom's more tbh. It's been a long long time when a post got me pis*sed as this one. Rant over.
La Porta I say go for it.

 

Here’s a corollary question: does anyone have a good video of what a stock dual pipe setup from a GT or K code sounds like?

 

Wrong forum for that question.....
I may be surprised but I doubt you'll find many VMF members with stock dual exhaust.

 

I vote the Arvinode. I yanked Dronemaster 40’s and put Arvinodes on and love it. 2” all the way out to GT trumpets. At idle and cruise it’s extremely polite. Acceleration is quite proud and sounds incredible. I love putting my foot in it! As that video showed long hard acceleration is quite loud but be real with yourself. On the street, how long can you really pull a WOT run? Right to the next red light is my guess. Or maybe a long on-ramp, but then it’s foot out and back to cruise. It’s pricey for fossilized tech but the fact it’s available today is pretty cool. Plus, if you dislike it just change it out. It’s only money…

 

@69RR said it very well, opinions and holes, etc.
Do what you want because YOU want it, not because someone else likes it or doesn't, to spite or please anyone, to make or keep a friend or enemy. Who is earning and spending the money? Who is going to ride in it? It's your car. Enjoy it.

 

I feel bad for all those who have droning Flow
masters. We did hundreds of system installs
and sold hundreds of undercar setups via
phone/mail and only recall one customer
returning for 3-chambers vs the 2-chamber
system we originally did for them.
There is some science to the system layout,
none of which I understand. All I know is that
my setup done in ‘89 also doesn’t drone.

 

If you run a 16" muffler on one side and a 14" on the other, no drone. A dual exhast is a tuning fork. Don't let it be one. **** up it's day by making it asymmetrical.

You can also run more than one muffler. You can slip race bullets in.

My car sounds badass with side exit glasspacks. No drone whatsoever. It's not possible because they aren't tin cans. Not complicated. No tricks.

I heard a car and said I want my car to sound like that and I made it so. That's it.

 

One of the best "modifications" I did when I went through the rebuild and transmission swap was budget the money for the Arvinode system. Even though it was only a short-term option on 65s, I had absolutely no regrets installing it on my 66. As has already been opined, the sound is quite mellow and unnoticeable at normal cruising speeds. It will turn heads when you smash the go pedal.

I bought the complete "concours" system through NPD sans hangers as they were not available at the time. I brought the system to my local exhaust shop, and they installed for about $250 in 2017 dollars. Already had the HiPo exhaust manifolds along with the H-pipe installed, also sourced through NPD. YMMV

Go for it ! ! ! !

John

 

One of the best "modifications" I did when I went through the rebuild and transmission swap was budget the money for the Arvinode system. Even though it was only a short-term option on 65s, I had absolutely no regrets installing it on my 66. As has already been opined, the sound is quite mellow and unnoticeable at normal cruising speeds. It will turn heads when you smash the go pedal.

I bought the complete "concours" system through NPD sans hangers as they were not available at the time. I brought the system to my local exhaust shop, and they installed for about $250 in 2017 dollars. Already had the HiPo exhaust manifolds along with the H-pipe installed, also sourced through NPD. YMMV

Go for it ! ! ! !

John

Im with you on this. Mine cost about 300 bucks to have my local garage install it. If I want to I can change the heads and go with some aftermarket headers along with 2.5 inch pipes but it goes fast enough with the 347 and svo heads and sounds awesome!

 

I did the economy kit through NPD. Having not been born when the OG’s existed I have no experience with their sound or if it’s different. Waldrons mentioned to me their repro sounds the same for either kit and it’s just a concourse thing to get the more expensive kit. I also didn’t buy the hangers since my exhaust guy said it’s way too much for something he can fab easily. I’m on stock manifolds and a well worn in 289, no equalizer just true duals.

 

My car had a 2.25 dual exhaust with quiet turbo mufflers when I got it. No crossover. Good sound on a stock 289 but pretty quiet under 4k rpm. I'd go on the highway and think that C-Code sounded pretty decent though. I remember looking at the Arvinode but I didn't see what it would do for me over the pretty standard/basic dual exhast I had. Definitely wasn't going to add power and it honestly sounds similar. I think the Arvinode is simply a cool exhaust to have. Like a Lemans cam. Liking the sound is a bonus. But I wanted to get a bit more aggressive and the performance of 2.5" and glasspacks is above reproach up to 500hp 363.

 

When does the Arvinode exhaust start getting loud? Is there an engine rpm where the exhaust would start to interfere with a conversation or listening to the radio?

 

I would say it’s less about RPM and more about throttle depth. Stomp on it and it wakes up but once you take your foot out and cruise it behaves.

 

Obviously it's a different engine and so forth, but I wonder, if you want it to sound like an '06-'09 maybe try out the factory installed mufflers from an '06-'09?

 

Part of that has to do with it where the crossover is and that the Mufflers are mounted right under the back bumper at the back of the system.