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ddavidv
ddavidv UltimaDork
4/14/24 7:46 a.m.

Currently in the midst of swapping a six for a 302 in my Falcon. This means I'll need dual exhaust (oh darn!). There are no kits available for my car/setup. I'll have a local exhaust shop make it, but I have some specific needs. Trying to navigate the endless choices of performance mufflers out there is daunting. The car will sport HiPo manifolds, not headers, due to clearance problems with the column shift. Originally these cars had a transverse muffler behind the axle, but I don't suppose that matters much. What I need:

Ground clearance (it will be lowered 1")

Cool sound, obviously

Not absurdly loud except WOT, because sleeper car

...and the big one--no interior 'boom' resonance. I plan on using this car for highway trips and don't want a constant drone. The Flowmaster system on my Mustang suffers from this.

School me. Point me to articles or videos. Whatever it takes. I'm a sponge awaiting a river of knowledge. smiley

AngryCorvair (Forum Supporter)
AngryCorvair (Forum Supporter) MegaDork
4/14/24 9:03 a.m.

I'd look at late model mustang take-offs to see what might package. You know the OE systems will flow and won't drone if you're able to keep the pieces in their approximate relative locations.

Ranger50
Ranger50 MegaDork
4/14/24 9:06 a.m.

It's a falcon, use 65-66 mustang stuff.

Pete. (l33t FS)
Pete. (l33t FS) MegaDork
4/14/24 9:08 a.m.

Run the largest resonators you can as close as possible to the engine as you can.

 

Smallest pipes you can get away with.  If the Internet says you need 2.5" pipe, run 2".

 

It would be a pain on a Falcon but make sure the pipes exit behind the car.  Some people love turndowns for some reason, those are a great way to trap noise under the car and direct it back at you.

Streetwiseguy
Streetwiseguy MegaDork
4/14/24 9:25 a.m.

If you are running the susopension low, there is some merit to running the transverse muffler.  Dual in, dual out, sounds less harsh than full duals.  I presume there is a small performance sacrifice, but you've already done that with the manifolds.

Rodan
Rodan UltraDork
4/14/24 10:20 a.m.

If you can fit them, Walker Super Turbos are reasonably quiet, and sound good.

Back in the early 1990s, we did a test of the Walkers back to back with Flowmasters at the dragstrip on my 5.0LX.  Since they bolted on behind the H-pipe we could do back to back runs after switching them out in the pits.  Zero difference in performance, just more noise with the Flowmasters.  This was on a car with headers, cam, etc. running low 12's.

tester (Forum Supporter)
tester (Forum Supporter) HalfDork
4/14/24 10:21 a.m.

You definitely want a cross over "H" or "X" in there for scavenging and bettering sound.

The location of the mufflers makes a big difference in drone as do the type of muffler. I would think a couple of small resonators in the exhaust would tend to help changing the frequency range of the exhaust and moving the drone up or down the RPM range. 
 

Walker Turbo style mufflers were way less drone than Flowmasters in my experience.  YMMV 

 

preach
preach UltraDork
4/14/24 10:28 a.m.

All you need to do is put a Flowmaster sticker on a 302 car and it will sound amazing. Maybe the best non flat plane crank v8 sound ever.

No Time
No Time UltraDork
4/14/24 10:39 a.m.
Streetwiseguy said:

If you are running the susopension low, there is some merit to running the transverse muffler.  Dual in, dual out, sounds less harsh than full duals.  I presume there is a small performance sacrifice, but you've already done that with the manifolds.

If performance is a concern, this configuration lends itself to using cutouts between the inlet and outlets to bypass the muffler like on some of the newer performance cars. 

TheRyGuy
TheRyGuy Reader
4/14/24 2:01 p.m.

If you're using the hipo manifolds and not headers, have you considered running a y-pipe with a single muffler?

I don't know how hot this 302 you're building is going to be, but a single with relatively close lengths to the merge point can sound good. It's what I run with a single 3" in and out cheap Summit Turbo muffler on a warmed over (cam, bigger valves, bowl job) 302 in my car. It's 2-1/2 from the shorty headers to the merge point. Could've/should've done 2-1/4.

Exits out past the bumper (this is key) with no drone, and sounds great with the cheap turbo muffler. Sounds glorious with the exhaust cutout open 😄. The single has a slightly higher pitch than a true dual or dual with an h-pipe, similar to an x-pipe, but not the same.

A 401 CJ
A 401 CJ UltraDork
4/14/24 2:13 p.m.
Rodan said:

If you can fit them, Walker Super Turbos are reasonably quiet, and sound good.

Back in the early 1990s, we did a test of the Walkers back to back with Flowmasters at the dragstrip on my 5.0LX.  Since they bolted on behind the H-pipe we could do back to back runs after switching them out in the pits.  Zero difference in performance, just more noise with the Flowmasters.  This was on a car with headers, cam, etc. running low 12's.

Which Flowmaster?  They make a bunch depending on how rowdy you want.

Trent
Trent PowerDork
4/14/24 2:23 p.m.

My hot take:

 

Single exhaust V8s sound better than true duals. 

 

I personally don't care for the two drunk 4 cylinders having a fist fight sound of true duals. An X pipe helps and gives the extraction benefits a single exhaust has built in. 

RonnieFnD
RonnieFnD HalfDork
4/14/24 2:34 p.m.
Trent said:

My hot take:

 

Single exhaust V8s sound better than true duals. 

 

I personally don't care for the two drunk 4 cylinders having a fist fight sound of true duals. An X pipe helps and gives the extraction benefits a single exhaust has built in. 

He's not wrong.  X pipe with three chamber Flowmasters.  Quiet as a stock exhaust until you step on it.

Rodan
Rodan UltraDork
4/14/24 3:32 p.m.
A 401 CJ said:

Which Flowmaster?  They make a bunch depending on how rowdy you want.

Pretty sure they were 2 chambers because that's all there were then (it was 1991 or 1992)... IIRC the 3 chamber came out a year or so later.

Pete. (l33t FS)
Pete. (l33t FS) MegaDork
4/14/24 3:41 p.m.

I am strongly biased against Flowmaster mufflers because they are not very quiet, and they are amazingly restrictive.

On the other hand, I measured under 1psi backpressure on a 750hp supercharged V8 (Chevy 6.0) that had a single 3" exhaust and two Magnaflows inline.  The customer had us remove one because it was too quiet smiley. Didn't affect horsepower, either. The Magnaflows are essentially just straight pipes as far as exhaust flow is concerned.

 

On a 950hp naturally aspirated V8 (555ci Ford), I built a dual exhaust with electric cutouts exiting straight from the headers, and 3" pipes downstream from the cutouts' Y pipes to a pair of Magnaflows.  It made zero difference on the dyno if the cutouts were open or closed.  Definitely sounded very NASCAR with them open, though!

Gearheadotaku (Forum Supporter)
Gearheadotaku (Forum Supporter) UltimaDork
4/14/24 6:02 p.m.

There is an episode of engine masters where they test 2 1/2 duals vs a well made single 3". The single won.

Make sure to use a "Y" not a "T" when you join the head pipes. Then its off to the transverse muffler of your choice. 

buzzboy
buzzboy UltraDork
4/14/24 7:10 p.m.
Trent said:

My hot take:

I personally don't care for the two drunk 4 cylinders having a fist fight sound of true duals.

My favorite (gas) engine sound! lololol

ShawnG
ShawnG MegaDork
4/14/24 7:53 p.m.

Flowmasters are great if you want to sound like a dumptruck.

The Magnaflow 2 into 1 on our 454 Suburban sounds great?

Which 302 sounds good? The early 302 or the 5.0L? The 5.0 firing order is different.

dj06482 (Forum Supporter)
dj06482 (Forum Supporter) UberDork
4/14/24 7:53 p.m.

I had a Magnaflow exhaust system on my '92 Mustang GT and it sounded great (with no drone). Note you don't whatever muffler was sold with the Magnapacks, because those were LOUD!

Streetwiseguy
Streetwiseguy MegaDork
4/14/24 8:03 p.m.

My 82 Camaro has a single 3", one big Dynomax with two outlets.

With a small blower and too much camshaft, it sounds fabulous.

Every time I have a choice, I install a Walker Dynomax super turbo muffler.  Or two.  

The best sounding 4 cylinder ever is a Datsun L20 with a 2 1/2 inch exhaust into a Dynomax.

But that's just my opinion, I could be wrong..

Gearheadotaku (Forum Supporter)
Gearheadotaku (Forum Supporter) UltimaDork
4/15/24 6:36 p.m.

I had a pair of Walker DynoMax super turbos on my '88 Corvette. Super loud and vibrated the whole car. They hit the trashcan as soon as the Corsa exhaust arrived. Those were sweet sounding mufflers.

Curtis73 (Forum Supporter)
Curtis73 (Forum Supporter) MegaDork
4/15/24 7:58 p.m.

I personally hate the sound of Flowmasters, however having said that, there were some Flowmaster Fox body kits that sounded pretty awesome.

Dynomax makes some not too expensive stuff that I like a lot.

Magnaflow makes some really high quality stuff (and you'll pay for it) but I get the impression they put more emphasis on quality materials and a really great sound, and they forgot that people actually ride IN vehicles, and controlling drone is a thing.  I get half deaf after driving my Van with a Magnaflow, but I will admit, it has the perfect sound outside.

I'll admit if I'm wrong, but I disagree with those who say to put the muffler or resonator as close to the engine as possible.  Acoustically speaking (on a cross-plane V8, anyway) you want the muffler at around 2/3rds the total length, and a resonator (if added) as close to the tailpipe exit as you can.  The reason is the overtone series, which is a ratio of total wavelength divided by halves, thirds, and sixths.  Ever slap your hand over the end of a tube and it makes a tone?  Ever notice that if you slap the tube versus leaving your hand on the end after you slap it, the tone it produces is an octave lower?  The tube makes a tone based on the pressure wave your hand gives it.  Removing your hand allows the column of air to dissipate its energy in both directions.  Leaving your hand there forces it to only expel its energy out one end.  It has effectively selected to only let you hear the lower octave from the other end, instead of hearing both from the near end.  Your engine does the same thing when the exhaust valve opens and closes.  It spits a pulse and then slams the one end shut.

The thing about standing waves and overtone series is that each division (halves, thirds, sixths) are attenuated at each interval.  The strongest overtone will be the first octave, but the following 2/3 overtone is much quieter.  By putting the muffler at the 2/3rds, you're effectively preventing the half (octave) wave, and placing the less-strong 2/3rds wave in the muffler.  By adding a resonator, you're effectively splitting the rear third of the exhaust into another 2/3 (or 1/6th the whole length)

The other reason I don't like putting a muffler close to the engine on a V8 is because of the highly variable pulses and frequencies the engine can create.  It's one thing on a 4-cylinder when you have four even pulses.  On a V8 you get  1-5-4-2-6-3-7-8, which makes it L, L, R, R, R, L, L, R.  The range of frequencies it can create WAY more craziness than a 4-pot.

The other big reason I like to leave some space to the muffler is because whatever frequencies DO make it through the muffler are now introduced to a whole additional tube, which can generate their own standing waves and overtones.  I let the exhaust make its noise, then muffle it near the end.

Another way to sculpt things is by using an X or H pipe.  That uneven distribution of exhaust pulses in the manifolds causes wild variations in exhaust pressures.  Adding a crossover pipe allows the extra pressures from one side bleed to the other, and vice versa.

If you're going for quiet, I'll echo the Walker Super Turbos.  They're good, cheap, and relatively quiet with a nice sound.  I would use them on a stock 302, but if you're building a really hot one, they'll be restrictive.

I'm sure you already know this, but bigger diameter is louder, and it's fine to step down one size after the muffler.  There is enough cooling in the tubing that the exhaust volume is reduced.  In some applications, it can actually help by being a better velocity match.  Straight through mufflers are also typically louder than offset.  I also agree with whoever said this above... if the internet says 3", do a 2.5".  The internet likes to base it on max hp, and a 2.5" might cost you 10hp at WOT and redline, but at least you'll be less angry at your life choices after a nice drive.

Example:  I'm building a 550-hp LS.  If I were racing it, it would get dual 3" that dump in front of the axle.  I'm not, so it's getting a full 2.5" out the back.  I would rather have 540hp and not be deaf when I get to my destination.

 

Curtis73 (Forum Supporter)
Curtis73 (Forum Supporter) MegaDork
4/15/24 8:06 p.m.

Also, if I'm not mistaken, a factory GT Fox achieved its 225 hp with a dual 2" that stepped down to 1-7/8"?  Or maybe a dual 2.25 that stepped down to 2?

My Impala SS had a similar setup for its 260hp

Curtis73 (Forum Supporter)
Curtis73 (Forum Supporter) MegaDork
4/15/24 8:10 p.m.

I would start trolling google for "mustang GT exhaust sounds" and you'll find eleventy quillion videos.  And trust me on this:  If the video starts looking like the first picture, don't waste your time.  WAY too close.  No one will listen to your exhaust from 3' away, and the recording will sound like snot.  If it starts looking like the second one, watch it.  That's how you and everyone else will experience it.

GPz11 (Forum Supporter)
GPz11 (Forum Supporter) HalfDork
4/15/24 8:12 p.m.

Running 4 Magnaflows under my 5.0 swapped XR4Ti.

Had 2 originally but my neighbor used my car as an alarm clock so that told me it was a bit too loud. Adding the 2nd set just toned things down nicely.

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