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Packing a MAC 4 into 1 Baffle with Fiberglass

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  • #1

    Packing a MAC 4 into 1 Baffle with Fiberglass

    Has anyone tryed to get more low to mid range from their MAC 4 into 1? I was thinking about removing the baffle and wrapping it with fiberglass mat and reinstalling it packed. Would this increase the back pressure allowing for a lower powerband? Wonder if their would be any advantage or disavantages by using a packed baffle?
    Maybe it would quiet them down a bit.
    "We are often so caught up in our destination that we forget to appreciate the journey." "
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  • #2
    It would definitely quiet them down, but back-pressure gain would be minimal.
    1979 XS1100F
    2H9 Mod, Truck-Lite LED Headlight, TECHNA-FIT S/S Brake Lines, Rear Air Shocks, TKAT Fork Brace, Dyna DC-I Coils, TC Fuse Block, Barnett HD Clutch Springs, Superbike Handlebars, V-Star 650 ACCT, NGK Irridium Plugs, OEM Exhaust. CNC-Cut 2nd Gear Dogs; Ported/Milled Head; Modded Airbox: 8x8 Wix Panel Filter; #137.5 Main Jet, Viper Yellow Paint, Michelin Pilot Activ F/R, Interstate AGM Battery, 14MM MC, Maier Fairing, Cree LED Fog Lights.

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    • #3
      If you just pack it without modifying the baffle then chances are you will restrict the system too much. The MAC baffle is not very 'open' as is.

      What I did with mine several years ago to try and give it a more mellow tone was this (sorry, I don't have any pics). First I sawed off everything in front of the rear plate leaving about 1" stub of the pipe ahead of the rear plate. Then I took a length of light-weight steel tubing, about 12" long, of the correct diameter to fit over the 1" stub. I carefully cross drilled many holes through the 12" long tube on a drill press and then brazed it onto the 1" stub. No front plate is needed because the packing centers the tube. Place a few wraps of muffler packing around the drilled tube and insert using the same screw that holds the baffle in.

      Doing this gave the little extra flow I needed with the carb, head and cam mods I have and rendered a very nice mellow tone, not unlike the old 'Cherry bomb' mufflers.

      The usual caveat...it worked for me...might not be right for you.

      Oh, and if you want to go back, just saw 1" off of the old baffle and the tube you installed and braze the baffle back in using the piece of tube as a ferrule.
      Mike Giroir
      79 XS-1100 Special

      Once you un-can a can of worms, the only way to re-can them is with a bigger can.

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      • #4
        I had a Mac 4 into 1 on my SF, they have a strange sound to them with that baffle. I took some exhaust wrap and wrapped it around the exit pipe inside, up against the back plate. The exhaust coming into the baffle blew up against the wrap and mellowed the sound a little and I'm sure it increased the BP some also.

        I tried some SS wool in there but it just kept blowing out the tailpipe.

        My SF was crazy fast through all ranges.
        Greg

        Everybody is a genius. But if you judge a fish by its ability to climb a tree, it will live its whole life believing that it is stupid.”

        ― Albert Einstein

        80 SG Ol' Okie;79 engine & carbs w/pods, 45 pilots, 140 mains, Custom Mac 4 into 2 exhaust, ACCT,XS850 final drive,110/90/19 front tire,TKat fork brace, XS750 140 MPH speedometer, Vetter IV fairing, aftermarket hard bags and trunk, LG high back seat, XJ rear shocks.

        The list changes.

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