Exhaust Exhaust for a 347???

Discussion in 'Fox 5.0 Mustang Tech' started by vpap1, Feb 25, 2013.


  1. vpap1

    vpap1 Member

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    OK current setup:

    347 10:1 comp. track heat intake and 170 cc heads, 30# injectors, TFS 2 cam, 80 maf 75 TB,
    BBK 1 5/8" short tube headers, into 2.5" non cat H pipe, into 2.5" flowmasters with no exaust pipes

    made 351 RWHP at 5500 rpm

    Upgrading the camshaft to a xfi236 ...and hoping with upgraded valve spring and retainers and headers with make in the 370's for RWHP at about 6100 rpm

    question is:

    1) Do I get a LT header with 2.5" collector and 2.5" x pipe and leave the 2.5" mufflers
    2) LT Header with 3" collector, 3" x pipe and upgrade to 3" mac pro dumps
    3)LT Header with 3" collector, 3" x pipe into a 2.5" reducer to the 2.5" flowmasters i currently have

    Possibly adding spray later on for the strip...

    What ya'll think?

    V
    #1
  2. MikeH686

    MikeH686 Mine is only two inches though.

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    Dont do the third one it makes no sense to reduce back down to 2.5 im going 1 5/8 to a 3 inch collector to a 3 inch x pipe and 3 inch dumps
    #2
  3. vpap1

    vpap1 Member

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    what do you have for power? @ what rpm? Thanks
    #3
  4. MikeH686

    MikeH686 Mine is only two inches though.

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    410 at 5700 rpm but that was on a carbed setup
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  5. clement

    clement Founding Member

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    the further back the restriction is the less negative effect it will have because the gas cools back down the further it travels. its not ideal. full 3" would be ideal, either way i wouldnt run a chambered muffler like a mac or flowmaster. the dynomax race magnum should pick up .2-.3 in this combo.
    #5
  6. vpap1

    vpap1 Member

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    who carries a 3" x pipe with flanges already welded on?

    V
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  7. 84Ttop

    84Ttop They make new pistons every day, so why worry? SN Certified Technician Mod Dude

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    My suggestion is 1 3/4 long tubes w/3" collectors and some dynomax ultra flow mufflers
    #7
    MikeH686 likes this.
  8. MikeH686

    MikeH686 Mine is only two inches though.

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    Bassani has a nice x pipe with ball and socket flanges
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  9. 2000xp8

    2000xp8 Mustang Master

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    My suggestion is to leave the exhaust the way it is and spend the money opening up the heads a bit which could possibly bring the power up around the 400 mark instead of 370.
    I know plenty of people that make over 400rwhp on 347's with similar exhaust setups as to what you have now.

    The guy i sold my entire 347 setup to, including my exhaust made 425rwhp and that combo was my extrude honed tw's ($750 for the extrude honing), rpII intake, custom cam, 1 5/8 mac shorties, offroad bassani x pipe, 30's 80mm pro m.
    Literally i sold everything i had to fund my 4.6.

    Buying all new exhaust parts is going to set you back quite a bit for what you are going to get. That money for sure would be better spent cnc'ing the wedges.
    #9

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