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Dual 3" with headers

Discussion in 'The Garage' started by dammit32, Jul 1, 2003.

  1. dammit32

    dammit32 1/2 ton status

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    Dual 3\" with headers

    I am thinking of doing headers and retaining my 3" pipes on the drivers side...will it have enough back pressure if I add the 3" pipes on the passenger side to create duals?.
     
  2. gruveb

    gruveb Registered Member

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    Re: Dual 3\" with headers

    You planning on building that thing to run in the 10 second bracket? If not, then that exhaust is way to big! 2 1/2" duals is actually a little large.

    Most street/strip cars that can run in 12's or better run 2 1/2" duals around here.

    I've got 2" duals on there right now (without a balancer tube), and when I rebuild it, I'm gonna stick with 2".
     
  3. CHEVY 4WD

    CHEVY 4WD 1/2 ton status

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    Re: Dual 3\" with headers

    Everyone will tell you 3in is to big
    BUT if you have a pretty healty SB its fine but if your headers wont accept a 3in pipe go a few feet of 2.5 then step it up to 3 Big exuasy wont sound as raspy though more hollow
     
  4. gruveb

    gruveb Registered Member

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    Re: Dual 3\" with headers

    A 3" exhaust with 2 1/2" pipes somewhere along the line isn't any better than just a 2 1/2" all the way around, but it will sound louder, same way a megaphone works. But the 2 1/2" section will act as a bottle neck. The closer to the engine the bottle neck is, the greater effect it will have also.

    Consider the headers. If you're running headers that are 1 1/2" at the primaries, a 3" exhaust is likely a large waste of money.

    Nothing runs worse than an engine with mismatched parts, I've learned that the hard way!
     
  5. beater74

    beater74 1/2 ton status

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    Re: Dual 3\" with headers

    if it's a stock or half way modified SBC it's gonna get lost with 3" duals, sh!it 2 1/2 is to big. i'd go no bigger than 2 1/4" duals.
     
  6. CHEVY 4WD

    CHEVY 4WD 1/2 ton status

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    Re: Dual 3\" with headers

    If your header wont take anything bigger then 2½ then you only have about 2ft of that then 3in it will flow better
     
  7. blasterD

    blasterD 1/2 ton status

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    Re: Dual 3\" with headers

    The problem with dual 3" is that you lose all of your exaust velocity. Given a set amount of fumes exiting the engine, a smaller pipe will have more velocity. Velocity is important for cylender scavenging and low end torque. Scavenging is when the exaust traveling through the tube actually creates a vaccuum on the cylender to pull exaust out and suck fuel and air in. I have found that for a chevy 350, dual 2 1/4" pipes are ideal for an engine that is operated below 5500 RPM. /forums/images/graemlins/thumb.gif
     

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