How to quiet down my 3" exhaust?

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DrCharles

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I must be too old, because it's too loud. (More accurately, I prefer to speak softly and carry a big stick) :p

Anyhow, my 451 Dart has quite a rumble with headers, dual 3" with X-pipe and full tailpipes, Summit "turbo" mufflers in the stock locations, and glasspacks under the trunk floor for resonators. The tailpipes are just turn-downs stuck in the ends of the glasspacks, but come out the rear.

There is a fuel cell in the trunk, so plenty of room for additional mufflers under the trunk.Will replacing the glasspacks with another pair of mufflers help? I want to re-do as little of the piping as possible.
I could put long-case oval Walker mufflers under there.

DSCF0188.JPG
 
Oh the irony on this one.... I said it before someone else does...

With that being said Flowmaster had I believe a 60 series one time that were crazy quiet. I had them on a 540 for a short period and you would have never known about the powerplant they were so quiet. However they did stifle it on the Chassis dyno...

JW
 
With that being said Flowmaster had I believe a 60 series one time that were crazy quiet. I had them on a 540 for a short period and you would have never known about the powerplant they were so quiet. However they did stifle it on the Chassis dyno...
I definitely want to keep it free-flowing (the 451 is probably near 500 hp at the moment, and quite a bit more when I put the massaged aluminum heads on this winter that flow 293.5 cfm).
There is room for almost any muffler under the trunk...
Doesn't Flowmaster have a 70 series too?
 
I definitely want to keep it free-flowing (the 451 is probably near 500 hp at the moment, and quite a bit more when I put the massaged aluminum heads on this winter that flow 293.5 cfm).
There is room for almost any muffler under the trunk...
Doesn't Flowmaster have a 70 series too?

You corrected me. That's the one. It's crazy long. But it will quiet you down. With you making more power upgrades, tread lightly on the idea of making it quieter. It will be interesting to see what others have to say about the matter....

JW
 
GEt rid of the glasspacks . Flowmasters reduce sound by cancellation . I suggest Magnaflow uses the absorption method . THat is , at low speeds it's quiet and sound increases as rpm goes up . So if you are cruising along Magnaflows are quieter than Flowmasters until youh it the loud pedal .
 
I must be too old, because it's too loud. (More accurately, I prefer to speak softly and carry a big stick) :p

Anyhow, my 451 Dart has quite a rumble with headers, dual 3" with X-pipe and full tailpipes, Summit "turbo" mufflers in the stock locations, and glasspacks under the trunk floor for resonators. The tailpipes are just turn-downs stuck in the ends of the glasspacks, but come out the rear.

There is a fuel cell in the trunk, so plenty of room for additional mufflers under the trunk.Will replacing the glasspacks with another pair of mufflers help? I want to re-do as little of the piping as possible.
I could put long-case oval Walker mufflers under there.

View attachment 1715634289

I swapped a set of these into my '68 when it was too loud.

Oddly the same e mufflers that were too loud on my '68 are much quieter on my '70. Both have TTI 3 inch full exhaust & headers, but the '70 is a 493" big block and the '68 a 408" stroked Magnum.

I also like to run ovalized megaphone tips on my cars, especially the electric cutout pipes. It improves the exhaust note much for the same reasons most wind instruments are designed with a flared end.

Super Turbo™ Mufflers - DynoMax® Performance Exhaust
 
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Power sticks will take about 5db off of it. Straight through design, no packing materials.
 
Power sticks will take about 5db off of it. Straight through design, no packing materials.
Those don't look like they'll flow very well, with those louvers sticking into the stream? Although that's less important at the end of the exhaust system.
I know some have run 3" to the mufflers and 2.5" tailpipes with little if any power loss, but significantly quieter. I don't want to redo the tailpipes though.
 
Frankly Doc, what you have now is what i would have recommended to someone else as a way to quiet down a too-loud system. The turbos are quieter than same-size chambered (flowmaster or clones) or straight-thru (ultra flow or glasspacks). I dont think a second set that far back will have much more effect than the glasspacks/resonators you are using now
I would think that your best bet would be a large quieter muffler, triple pass, in your stock location. Maybe a hemi muffler, or one of the big walker/dynomax/magnaflow versions.
I am using a pair of 50series fm big block on my 62, 5x12x22" case, also with a fuel cell in the trunk. But if yours is too loud with turbos, i dont think they are quiet enough for you. I also have a 3" 70 series fm big block that is very quiet, but it is in a single exhaust system (dually pickup with a cat). I also have a looong case magnaflow 3" that is fairly quiet for a staight thru.
The secret (at least in my humble opinion) to a great flowing quiet system is..... large tubing size, and the longest biggest case muffler you can fit under the car.
 
Frankly Doc, what you have now is what i would have recommended to someone else as a way to quiet down a too-loud system.
Hmm. Perhaps I should just work on sound-insulating the (former) back seat area! :) It's really not very loud behind the car (or so I've been told).

I would think that your best bet would be a large quieter muffler, triple pass, in your stock location. Maybe a hemi muffler, or one of the big walker/dynomax/magnaflow versions.
...
The secret (at least in my humble opinion) to a great flowing quiet system is..... large tubing size, and the longest biggest case muffler you can fit under the car.

I agree, a bigger muffler is the approach I'm looking for - but as you know, the space allocated for mufflers under an A-body is rather limited.
Why wouldn't a second muffler work, if the pulses are still audible coming out of the first one?
 
I didn't even install a stereo, because I knew I wouldn't be hearing it clearly anyway :rolleyes: Besides, I like the sound of the 451, just not quite so MUCH of it!

Jdsduster, what exactly are you disagreeing with, and what do you propose instead?
 
I think a second muffler would help, but you already have a second muffler in place. I dont think the change from the glasspacks to another turbo will be very dramatic.
Come to think of it, an acquaintance had a pair of large mufflers (in his case, only one pair) installed under the trunk where the gas tank used to be in his demon. It was a fairly quiet, smallblock stroker, 9second streetcar.
 
A second set of turbo mufflers as long as you can stand would be my choice. For that matter the magnaflow style should help as well.

Not a direct comparison but my D150 was obnoxious loud with headers, flowmaster y-pipe and a 3" single exhaust with a summit racing 3" in/out straight through muffler. Unbearably loud at WOT . I put a 3" Dynomax super turbo in line just after the straight through muffler and before it goes over the axle and it is night and day difference. Arguably the best sounding exhaust I have run on anything.
 
I put Hooker Aerochamber mufflers on my Dart when my dynomax turbos starting sounding like crap. The Aerochambers are pretty mellow.
 
My 68 Barracuda has full length, no crossover at all, dual 3" Dynomax crimped 3-pass turbo muffs, on the 400hp 367, with dual 3" over the axle tail pipes and turn downs.
The further the throttle valves are open, the louder it gets. At WOT and after 3500 she is a screamer. But people say from behind or on the sidewalk, it's a good scream. (well it's long anyway, because I use the GV as a splitter, and when she hits the rev-limiter, I just keep it there for 5 or 6 or sometimes 7 seconds,lol)
I have always had 3.55s (mostly), and in the beginning I had small tires, so it used to cruise at 65=3050(manual trans), which,long term, I found unacceptable. So I slowed down and cruised a few years at 56=2620, which was sorta doable,on my 20 minute commutes.
I then installed,some taller tires for 60=2560, but when those wore out,
I eventually installed a GVod, and 295/50-15s, and she now cruises very pleasantly at 65=2230; getting progressively louder with speed. But you know, a lot of that is wind-noise, as the ol' Plymouth bulldozes a hole in the atmosphere.

If I could do it over, I would put much smaller duals on it and cutouts, cuz daymn, those 3s are heavy. I think the pipes and muffs alone were 72lbs.
 
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If it were me I would shitcan the resonators lose the summit turbo Mufflers that are loud annoying and put on some Dynomax Ultra flow's
 
Dr. Charles, I bet I have what you need: 3" Dynomax VT mufflers. We have set on a 408 68 Barracuda and you'd be amazed at how quiet they are for such a short case. No resonation. If you have big cam, you may hear some minor tapping as the valves flutter but likely mounted under the trunk, you would not.
 
I once quieted a 340 enough to make the cops happy, by sliding a 2ft rolled up sheet of corrugated cardboard into the ends of the straight-section tailpipes, and anchored them with nails dropped thru the tops of the pipes. It passed.
I drove around the block and pulled the nails out, hit the gas and fired that cardboard right into last Thursday,lol.
I was maybe 22 years old.
 
Cute story, until the cops pull you over again for the same issue...

I'm not doing it because it's too loud for law enforcement (it's not, especially at cruise and idle), but because the noise annoys me :p
 
cardboard is free .....
Tickets aren't :rolleyes: (well, fix-it tickets may be).
Anyway, I've gotten some actual suggestions so now I need to look under the trunk floor and see what I can fit with the least work.
Unfortunately I ran the glasspacks pretty close to the springs; it's where the tailpipes came out. So a large oval muffler may have to hang lower (below the level of the spare tire well).
 
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