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Thread: dual exhaust

  1. #1
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    Default dual exhaust

    looking to two options to build exhaust for 5.0L 331 stroker
    I have SS 2 1/2'' shorty

    i need everything from the shorty on back.

    opt 1
    buy rock auto stuff for 87 Linc towncar
    -has 2'' hPipe and everything else

    opt 2
    purchase JD Squared https://www.jd2.com/model-32-bender
    which makes manually bending 2 1/2 pipe easy for diy use.
    allows me to custom bend pipe from now on.


    question-
    for all the theories and facts about savaging ect, if stock 2'' hpipe is used, would this be sufficient for my 331 since "both" pipes are being shared by way of the 2'' h pipe?
    meaning i have both 2'' pipes in the exhaust game ,, seems like separate 2 1/2'' pipes is smaller than 2 ) 2'' pipes with an integrated H pipe.

    i would rather buy bolt on stuff than to bend up pipe on my own.
    i think i will have the same amount of money in both options,, and with option 2 i have a new cool tool

  2. #2
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    You can also use Mustang stuff. It was a long time ago when I did it so I don't remember if had to add legnth to the extension tubes (H to Muffler) in addition to adding legnth to the tails. Otherwise it was bolt on. I have since reverted to a 3" single for my turbo application.

    John

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    but,, does my thoughts add up....
    doing 2'' with an H pipe suffice for the application?

  4. #4
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    2.5" pipes all the way back. Use Mustang stuff, lengthen where appropriate.
    '88 Thunderbird LX: 306, Edelbrock Performer heads, Comp 266HR cam, Edelbrock Performer RPM intake, Edelbrock 70mm TB, 76mm C&L MAF, 30lb injectors, 2.5" exhaust, AOD with 2800 PI converter, 8.8 with 3.73 gears, 31 spline Traction-Lok, 31 spline Moser axles, 04 Cobra front arms, Maximum Motorsports extreme duty rear arms, subframes.
    '11 Focus, '12 Mustang 3.7, '17 Accord EX-L V6

  5. #5
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    The short answer is yes it will likely suffice. But don't think of the H pipe as a second exhaust pipe. If it were a Y or X your absolutely correct. The H works more like a pulse dampener to control sound.

    The long answer is much more involved and I think your going to choke the engine at high load and rpm. I came across this site while looking for flow rates of different diameter pipes and it saves me alot of typing. I think it will pretty much answer most of your questions.
    http://www.exhaustvideos.com/faq/how...pipe-diameter/

    John

  6. #6
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    it does

    see here the link for full system. and below a screen shot of the hpipe
    https://www.rockauto.com/en/moreinfo...sn=472&jsn=472


    am i ok to use the smaller 2'' if this Hpipe is full dual? since each engine head is able to uses both pipes?

    or do the studies show the X pipe is better?
    Attached Images Attached Images

  7. #7
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    also on that article,, not sure he is accounting for static losses,, as in the total number of degrees the exhaust path has experienced before it can get out.

  8. #8
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    Quote Originally Posted by jcassity View Post

    am i ok to use the smaller 2'' if this Hpipe is full dual? since each engine head is able to uses both pipes?

    or do the studies show the X pipe is better?
    That's not really how it works. Each head is able to use both pipes, but not at once. What you are getting with the H/X pipe setup is a transition that allows the exhaust pulses to essentially travel the path of least resistance. The idea is to allow the gas pulses to change direction at the crossover if there is a lower pressure area on the opposite side to "pull" it out, creating scavenging. Kiiiiiiinda like slip streaming or drafting on the highw--- I mean racetrack....

    This is why an X pipe is generally considered a more efficient crossover design as it allows the gases to more easily change direction gradually if necessary, without taking a sharp 90* bend through a separate pipe like an H setup. The "drawback", if you can call it that, is that an X pipe has a smoother output sound whereas an H pipe will have a bit rougher sound. The difference in HP on the dyno is usually slim to none though.

    This is why 2+2 does not equal 4 when talking about crossovers. It is absolutely better than running a "true dual" setup with no crossover but still shouldn't provide the flow capacity of a full 2 1/2 system. If it were me, I would go with 2 1/4 if possible. I have seen tests done that even in 400+ hp engines, the upgrade to full 3" dual was a negligible gain on the dyno. You could probably get away with 2" if you're not doing any major engine mods but it kinda depends on the HP output that you are looking to achieve as that will determine how much air/exhaust gases will be flowing. As long as you're not maxing the flow capacity of your exhaust system any size upgrades beyond that will not make enough difference to be worth it.

    Looking at the chart posted above, I would say 2" - 2 1/4" should be sufficient...
    Last edited by sarjxxx; 06-13-2018 at 06:27 PM.
    --Steve
    1988 Cougar V6
    2012 F-150 3.7L
    2011 Mustang 3.7L

  9. #9
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    That's an H-pipe for a town car, and it won't fit. The H for the Mark VII will fit, but it's really not adequate (was barely adequate for a stock HO). You want the 2 1/4 Mustang H at MINIMUM. 2 1/2 is best, combined with same size cat-back using extended Mustang mids and tails. You can go from mild to wild on mufflers, but a pair of good 2.5 in/out turbo mufflers will sound nice without being loud or unacceptably restrictive up high.
    1988 Thunderbird 5.0
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  10. #10
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    You can order all the stock stang stuff at AutoZone.

    Get yourself a h-pipe for cheap from a place like jegs or summit, then you can order all the 2 1/4 - 2 1/2" stuff for cheaper then most stuff you'll find online.

    Ps, if ford thought that a 2" pipe was plenty, then they wouldn't have put 2 1/4" on a stock stang. Hp doesn't always increase on a dyno with bigger/more exhaust, but the acceleration of the engine does.

    If a 1/10 is gonna make a difference, go 3" and don't look back. Otherwise, stick to easy cheap and available parts that bolt right up and work.
    Quote Originally Posted by jcassity
    I honestly dont think you could exceed the cost of a new car buy installing new *stock* parts everywhere in your coug our tbird. Its just plain impossible. You could revamp the entire drivetrain/engine/suspenstion and still come out ahead.
    Hooligans!
    1988 Crown Vic wagon. 120K California car. Wifes grocery getter. (junked)
    1987 Ford Thunderbird LX. 5.0. s.o., sn-95 t-5 and an f-150 clutch. Driven daily and going strong.
    1986 cougar.
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