How to quiet down my 3" exhaust?

Mopar Exhaust Systems

  1. DrCharles

    DrCharles Well-Known Member

    Messages:
    1,007
    Likes Received:
    772
    Joined:
    Jun 7, 2012
    Location:
    West Plains, Mo.
    Local Time:
    12:31 PM
    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
     
  2. SLOPAR72

    SLOPAR72 Well-Known Member

    Messages:
    2,250
    Likes Received:
    1634
    Joined:
    Jan 5, 2016
    Location:
    Richmond, VA.
    Local Time:
    1:31 PM
    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
     
  3. DrCharles

    DrCharles Well-Known Member

    Messages:
    1,007
    Likes Received:
    772
    Joined:
    Jun 7, 2012
    Location:
    West Plains, Mo.
    Local Time:
    12:31 PM
    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?
     
  4. SLOPAR72

    SLOPAR72 Well-Known Member

    Messages:
    2,250
    Likes Received:
    1634
    Joined:
    Jan 5, 2016
    Location:
    Richmond, VA.
    Local Time:
    1:31 PM
    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
     
  5. Treblig

    Treblig Well-Known Member

    Messages:
    6,473
    Likes Received:
    3648
    Joined:
    Oct 5, 2013
    Location:
    South Texas
    Local Time:
    12:31 PM
     
  6. 383Scampman

    383Scampman Well-Known Member

    Messages:
    1,680
    Likes Received:
    899
    Joined:
    Nov 24, 2013
    Location:
    New Hampshire
    Local Time:
    1:31 PM
    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 .
     
    • Agree Agree x 1
    • jbc426

      jbc426 Well-Known Member

      Messages:
      1,879
      Likes Received:
      685
      Joined:
      May 30, 2007
      Location:
      West Coast
      Local Time:
      10:31 AM
      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
       
      Last edited: Nov 21, 2020 at 2:57 PM
    • ch1ll

      ch1ll FABO Gold Member FABO Gold Member

      Messages:
      768
      Likes Received:
      268
      Joined:
      Jun 12, 2009
      Location:
      Belgium,wi
      Local Time:
      12:31 PM
      Power sticks will take about 5db off of it. Straight through design, no packing materials.
       
    • DrCharles

      DrCharles Well-Known Member

      Messages:
      1,007
      Likes Received:
      772
      Joined:
      Jun 7, 2012
      Location:
      West Plains, Mo.
      Local Time:
      12:31 PM
      Aren't those the same as the Summit turbo mufflers though?

      How about another pair of turbo mufflers in place of the glasspacks... any problem with putting them in series?
       
    • DrCharles

      DrCharles Well-Known Member

      Messages:
      1,007
      Likes Received:
      772
      Joined:
      Jun 7, 2012
      Location:
      West Plains, Mo.
      Local Time:
      12:31 PM
      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.
       
    • 33IMP

      33IMP Well-Known Member

      Messages:
      404
      Likes Received:
      400
      Joined:
      Jul 3, 2020
      Location:
      Taxifornia, soon 2b arizona
      Local Time:
      10:31 AM
      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.
       
    • DrCharles

      DrCharles Well-Known Member

      Messages:
      1,007
      Likes Received:
      772
      Joined:
      Jun 7, 2012
      Location:
      West Plains, Mo.
      Local Time:
      12:31 PM
      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 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?
       
      • Disagree Disagree x 1
      • jazak5

        jazak5 Well-Known Member

        Messages:
        950
        Likes Received:
        429
        Joined:
        Aug 6, 2015
        Location:
        NY
        Local Time:
        1:31 PM
        upload_2020-11-21_17-42-14.jpeg or images?q=tbn:ANd9GcTIbrRD2xqBR_tCVsOz2BWTfobGgFjFv6VPQg&usqp=CAU.jpg :rolleyes:
         
      • DrCharles

        DrCharles Well-Known Member

        Messages:
        1,007
        Likes Received:
        772
        Joined:
        Jun 7, 2012
        Location:
        West Plains, Mo.
        Local Time:
        12:31 PM
        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?
         
      • 33IMP

        33IMP Well-Known Member

        Messages:
        404
        Likes Received:
        400
        Joined:
        Jul 3, 2020
        Location:
        Taxifornia, soon 2b arizona
        Local Time:
        10:31 AM
        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.
         
      • 496 polara

        496 polara moparts id gch

        Messages:
        433
        Likes Received:
        196
        Joined:
        Feb 23, 2014
        Location:
        North Carolina
        Local Time:
        1:31 PM
        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.
         
        • Agree Agree x 1
        • Vertex_Jeff

          Vertex_Jeff Undocumented Mopar Guy

          Messages:
          97
          Likes Received:
          174
          Joined:
          Nov 10, 2019
          Location:
          Richmond IN 47374
          Local Time:
          1:31 PM
          I put Hooker Aerochamber mufflers on my Dart when my dynomax turbos starting sounding like crap. The Aerochambers are pretty mellow.
           
          • Agree Agree x 1
          • AJ/FormS

            AJ/FormS 68 B'cuda fb, Form S clone ... 367/A833/3.55s

            Messages:
            19,419
            Likes Received:
            7252
            Joined:
            Jan 19, 2014
            Location:
            South-Central Manitoba,Canada, 900ftelevation
            Local Time:
            12:31 PM
            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.
             
            Last edited: Nov 22, 2020 at 11:49 AM
          • MOPAROFFICIAL

            MOPAROFFICIAL FABO Gold Member FABO Gold Member

            Messages:
            6,759
            Likes Received:
            5711
            Joined:
            Jun 1, 2016
            Location:
            Beach
            Local Time:
            10:31 AM
            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
             
          • VOETOM

            VOETOM Well-Known Member

            Messages:
            911
            Likes Received:
            342
            Joined:
            Jul 27, 2008
            Location:
            KC, MO area
            Local Time:
            12:31 PM
            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.
             
          • AJ/FormS

            AJ/FormS 68 B'cuda fb, Form S clone ... 367/A833/3.55s

            Messages:
            19,419
            Likes Received:
            7252
            Joined:
            Jan 19, 2014
            Location:
            South-Central Manitoba,Canada, 900ftelevation
            Local Time:
            12:31 PM
            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.
             
          • DrCharles

            DrCharles Well-Known Member

            Messages:
            1,007
            Likes Received:
            772
            Joined:
            Jun 7, 2012
            Location:
            West Plains, Mo.
            Local Time:
            12:31 PM
            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
             
          • AJ/FormS

            AJ/FormS 68 B'cuda fb, Form S clone ... 367/A833/3.55s

            Messages:
            19,419
            Likes Received:
            7252
            Joined:
            Jan 19, 2014
            Location:
            South-Central Manitoba,Canada, 900ftelevation
            Local Time:
            12:31 PM
            cardboard is free .....
             
          • DrCharles

            DrCharles Well-Known Member

            Messages:
            1,007
            Likes Received:
            772
            Joined:
            Jun 7, 2012
            Location:
            West Plains, Mo.
            Local Time:
            12:31 PM
            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).
             
          • 383Scampman

            383Scampman Well-Known Member

            Messages:
            1,680
            Likes Received:
            899
            Joined:
            Nov 24, 2013
            Location:
            New Hampshire
            Local Time:
            1:31 PM
            I meant Dynomax . Sorry if there is any confusion .
             
          1. This site uses cookies to help personalize content, tailor your experience and to keep you logged in if you register.
            By continuing to use this site, you are consenting to our use of cookies.