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Getting new exhaust- Single versus dual exhaust?

Discussion in 'The Garage' started by 87GMCJimmy, Feb 25, 2003.

  1. 87GMCJimmy

    87GMCJimmy 1/2 ton status

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    I'm finally having a new exhaust built. It's going to be from the exhaust manifolds on back. I've heard single exhaust it better for low end performance while duals is better for top end. This is going on a stock 5.7 vortec motor. I'll need dual cat's, 4 O2's and 1 or 2 50 series flowmasters.

    Thanks,
    Mike
     
  2. Highlander

    Highlander 1/2 ton status

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    When I get the money I'll be putting a single 3in on my 83. I've been told from more than one place a single 3in will out flow duel 2 1/4's. which is what I have right now.


    Eric
     
  3. MudNurI

    MudNurI 1/2 ton status

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    I had dual 3" put on mine....with my 305, single versus dual wasnt going to make much of a differnce in power...had it done at a custom shop- they did a great job, was big $ but worth it, nothing leaks, and sounds pretty darn good to boot

    Brandy
     
  4. DesertDueler

    DesertDueler 1/2 ton status

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    I would do dual since you have to run dual cats. Run dual 2.5" exhaust, it will outflow 3". Single exhaust is better for real low end, but dual gives you better all around power.

    Dan /forums/images/graemlins/burb.gif
     
  5. Hossbaby50

    Hossbaby50 3/4 ton status

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    I run dual 2 1/4" on mine. It helped out a fair amount on power. If I where you I would do duals. But the only thing is, if the emission nazi's in Phoenix catch you with dual (they are illegal for your truck) then you might have a problem. They have never said anything to me about mine though so I guess it doesn't really matter. Personally I would run 2-1-2 that way you are legal and you get a little of the best of both worlds.

    Run 2 pipes from the manifolds to 1 big high flow cat 3" cat (like off an F350) and then dual from there out. Legal, low end power, dual 50 series, and it will flow plenty.
     
  6. 87GMCJimmy

    87GMCJimmy 1/2 ton status

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    For legallity I must have dual cat's with with all 4 O2 sensors working. The truck must be emission to either the year of the motor or the year of the truck which ever is newer. I guess I need to figure out if on a 99 5.7 is it legal to put dual mufflers on it?

    Mike
     
  7. fortcollinsram

    fortcollinsram 1/2 ton status

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    The number of pipes doesn't matter...it is the size /forums/images/graemlins/thumb.gif A single 3" pipe has an area of 28.27^2 inches while a dual 2" system has an area of only 25"...For a vortec 350, I would go eith Single 3" or dual 2-1/4". If you do duals, will is be a TRUE DUAL system? On my 454, I am putting on a true dual system with 3" pipes and Thorley Tri-Y headers...thaat is an overall area of over 56^2"../forums/images/graemlins/thumb.gifAnyhow, I think it comes down to whats legal for you to do and what is cost effective...the price diffence b/w two sticksof 2-1/4" pipe and a single 3" stick of tubing is not that much...

    Chris
     
  8. sdavid

    sdavid 1/2 ton status

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    A '99 5.7L Vortec would have had dual pipes and dual cats going to one muffler and then one pipe going to the back after the muffler. That is what my '97 Z71 had with the same exact engine. I put a 50 series flowmaster on it that had dual inlets and outlets and ran dual pipes out the back, perfectly legal. Worked great other than being too quiet for my taste.

    If you have the money, get the headers. I think that is where you will find alot of performance help.
     
  9. Hossbaby50

    Hossbaby50 3/4 ton status

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    Personally I would have to say just go true dual. I have never had a problem with the emission nazi's in AZ over my dual exhaust. Every time i ever went to get my emissions done the just put the collectors pipes on my exhaust and did the test. They never looked underneith to see if I was running 1 or 2 cats. Legally I should only have 1 cat. They never said anything to me though, or even look for that matter.

    They thing that pissed me off is they failed me one time because my gas cap didn't pass the pressure test. /forums/images/graemlins/angryfire.gif the motor and everything else passed fine, except the gas cap.
     
  10. 87GMCJimmy

    87GMCJimmy 1/2 ton status

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    I just got off the phone with someone from the AZ emission place. They said that its against federal regulations to put daul mufflers on something that had a single. If I was just going in for the regular emission test I wouldn't be worried about it but b/c I'm putting in a different engine it when I get it registered again it needs to go though a different, more complete inspection first.

    Does anyone know if the 3/4 ton or 1 ton 1999 trucks with the 5.7 came stock with dual mufflers? If so I might be able to get around it. Otherwise it might be up to how picky the inspector is and it's really not worth it to chance it.

    Thanks agian,
    Mike
     

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