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Thread: Avanti floor muffler heat

  1. #1
    Speedster Member
    Join Date
    Jun 2013
    Moretown, Vermont

    Avanti floor muffler heat

    I'm worried about excessive muffler heat on my Avanti's fiberglass floor. I'm looking at using a FlowMaster Super HP 2 ... 4" X 5.63" X 18" (because my LS2 needs an"old school" tone and moderate sound) which is designed (with packing) to "control heat transfer". Avantis don't have heat shields under the front seat ... should I be worried (also because of my tight tolerances from using a 4" thick muffler)? I have cast iron headers, Cats, 2 1/4" SS exhaust pipes, no H pipe (yet) ... and also plan on using 12' Vibrant Bottle resonators to help control the trailing throttle and drone. Anybody?

  2. #2
    Silver Hawk Member
    Join Date
    Jan 2008
    Bay City, Mi., USA.
    I can't speak to drone etc with your setup but my 83 has a 2 1/4" Silvertone system with Magnaflow ss oval glass mufflers and it sounds great. It was far enough from the floor I wasn't concerned but on my 74 the system ended up closer to the floor and I added a heat shield above each muffler spaced away from the floor a bit. It was pretty easy as the floor was bare when I installed them. They are about 24 ga. Aluminum sheet.

    The 74

    Not the best shot but you can see them.

    I can get a shot of the 83 setup later if necessary.

    , ,

  3. #3
    Silver Hawk Member bezhawk's Avatar
    Join Date
    Jan 2008
    here, sometimes somewhere else
    There shouldn't be to much heat from the mufflers. Most of the heat in an Avanti is in the front, and transmission tunnel. Do everything you can to insulate inside, and it will help make the car much more enjoyable and solid feeling. On my last project, I used 3 layers of different heat and sound insulation.
    First, when the body was off, I sprayed the bottom with "Lizard Skin" heat barrier. Inside, I put down a layer of Dynamat with the heavy foil, Then I added a closed cell foam with an aluminum barrier over that. It is a duct insulation, and about 3/16". Then over that was a jute that has aluminized mylar on BOTH sides. then the carpeting. Inside the doors, I glued reconstituted rubber mat that was about 3/16" thick to cut down resonance, much like a Q pad body shops use. I also used some Cpap tubing to duct cool air from the cowl to the transmission shifter area. That is a factory fix they did on later cars.
    Bez Auto Alchemy

    "Don't believe every internet quote" Abe Lincoln

  4. #4
    Commander Member
    Join Date
    Jul 2016
    Kearney Nebraska
    I just order a 2"x 50' roll of exhaust wrap off of Amazon yesterday for $17. I plan to wrap the Avanti from the exhaust manifold to the muffler next week. I have used this product on other things and its been great!!
    Jim Kaufman
    Kearney NE

    1952 2R10
    1953 Champion (sold it and still kicking myself)
    1962 GT Hawk
    1963 R3984 Avanti R1

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