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3" vs Duals

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by grtwhite, Sep 30, 2000.

  1. grtwhite

    grtwhite 1/2 ton status

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    3\" vs Duals

    Time for a new exhaust on my 88 k5, trying to decided between a single 3" from the Y back or dual exhaust? Is it worth the hassle for duals. By hassle I mean finding a shop that doesn't have problems with emmisions and the tight fit of running 2 pipes ie. transfer case, plus the extra cash of 2 mufflers and cats. Also heard of trouble with the cossover pipe or H-pipe and the front driveshaft of guys with lifted rigs. How much extra performance is gained with the dual setup? More intersted in low end torque myself.
    - Jay
     
  2. 82Jimmy

    82Jimmy 1/2 ton status

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    Re: 3\" vs Duals

    why not 3in duals?

    Damn colors don't work!

    Damn colors don't work!
     
  3. jarheadk5

    jarheadk5 1/2 ton status

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    Re: 3\" vs Duals

    I read somewhere once that for low-end with a small-block, a single 3" is better than a dual 2 1/2" system. Something to do with backpressure, I think...

    Someone correct me if I'm wrong, because I'm curious, too.

    [​IMG] Semper Maintenance!
     
  4. blazer72

    blazer72 1/2 ton status

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    Re: 3\" vs Duals

    I had 3inchh duals with a 2.5 inch cross over behind the transfer case, I just went to an OEM 2.25 to single 3 inch y-pipe. It moved the tork curve down about 3oo to 500 rpm plus drop the over all sound leavl and drope the under truck heat build up!! As for the h pipe and the drive shaft I read some place way back to paint the pipes with spray paint start the motorlet it run till in was at temp trun it off and then place the h pipe were the paint stoped burnning off!!! Its what I did,

    I understand the jeep thing I drive a BLAZER!!

    Ken
     
  5. TX Mudder

    TX Mudder 1/2 ton status

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    Re: 3\" vs Duals

    I think a single 3" is better, unless you put an H-pipe in your duals.
    I have 2 1/2 duals and they are too loud, lus I don;t think they create enough backpressure for torque.
    When I get it done again I'll have a factory Y to a 3" single.
     
  6. 8_YOUR_H2

    8_YOUR_H2 1/2 ton status

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    Re: 3\" vs Duals

    I read in a recent Four wheeler where they tested the two different exhausts side by side. At 3500 rpm both exhausts produced the same horsepower on the test vehicle. However at rpm's up to 3500 the dual exhausts produced more horsepower. I Cant rember the figure but it was enough to make me think dual exhaust are the way to go for more low end power like what you are looking for
     
  7. Blazer79

    Blazer79 1/2 ton status

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    Re: 3\" vs Duals

    All I can say is that I have dual 2.5" and I'm very happy with them. The shop I used could only bend tubes 2.5" or smaller, so I took the "true dual" way with a 2.5" H-pipe as closer to the engine as possible, and that was behind the transfer case (NP203). There was no way of installing them before the tranny without losing ground clearance.

    I really don't feel I lost any low-end torque, and feel I gained a lot in the 3000 rpm and higher. But add to that figure a set of Flowtech Afterburner headers and a pair of Flowmaster 40 series. Those other items have a lot to do in the final power equation.

    <font color=blue>//////
    http://blazer79.coloradok5.com
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  8. rich'90

    rich'90 1/2 ton status

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    Re: 3\" vs Duals

    I have 2 1/2 dual also. I did not notice the change in power that much. Routing was not that much of a problem if you find a good shop. The noise is up though. Good luck.

    go heavy or go home
     
  9. Blue85

    Blue85 Troll Premium Member

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    Re: 3\" vs Duals

    If you have the transmission brace "rod" on the passengers side, then the routing will be tight on that side. Otherwise, there is plenty of room everywhere for a full dual. I had to put my crossover pipe under the tailshaft of the T-case. I'm not sure how these guys are putting it further forward. Under the tranny?

    '85 JIMMY
    '90 paint/grill/trim 5"susp 33/12.5/16.5
    Fresh 350 B&M '87 TH700
     
  10. 88blazer

    88blazer Registered Member

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    Re: 3\" vs Duals

    About the backpressure thing, that is wrong. Here is the best explination I can find. http://personal.riverusers.com/~yawpower/techindx.html

    It is for rotary engines, but the same basic principal applies to boingers. Boinger is the term Mazda used to describe the wasted up and down motion of pistion engines compared to the rotary. (I can here the responses to that comment now.) [​IMG]

    Read the Jan and Feb articles closely then you will understand why dual 3" pipes is a bad thing for a low RPM truck engine.

    Remember area = 3.14*r^2
    Dual 2 1/4" pipes have more area than a single 3".
    IMHO, for best overall power, go for dual 2 1/4" pipes and full length headers.

    Hit? Those tires rub . Rubbin' is off roadin'.
    http://personal.psu.edu/bjh182
     

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