Enjoy the loss of torque. Seriously. Unless you're running 1.75-2" pipe, you will lose power. And you need a crossover, either H or X will work, for proper scavenging.

 

Ya need to listen to Horatio!

Before I got my V8, I had a 3.9 and has a single 2.5" exhaust on it. My Dad also has a 3.9, but he put duals on it, and HATES THEM! You can't get it to sound good, and it KILLS your lowend.

If you want dual pipes, wait and build the motor. But if you STILL want to do duals, atleast do a single in dual out muffler...

 

First off, I dont think he wants duals. I think he wants a single in dual out which I just got on my 3.9L 97. Its a flowmaster 40 series. I have 2.25 pipping with a single in and dual tips coming at a 45degree on my bumper. My low end is not much different. All this talk of dramatic low end torque will be lost and so on and so forth: its not. Plus the kid is going to have to worry about 10 LB of torque lost unless he is running it down a quater mile so I would say do it. The 40 series I got sounds nice and throwtie and I love it. So my advice to you is just to do it if you want to. Its a truck, not a pace car so have fun with it. O and the mufflar gave me 13 more HP.

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Did you dyno your truck before and after?

You only think it gave you 13hp. Flowmaster tests their mufflers and the design gives a peak gain of 13 hp under ideal conditions. I doubt that it would provide that much of a gain on every different vehicle that a person could put the muffler on. And it's not always 13 hp at the power peak, it could actually hurt the peak power level while adding 13hp somewhere else in the curve. Or it could be 13hp gained on a car that had X other mods that help to move air in and out, or no cats... it's a case of "this muffler has made 13hp" not "this muffler will give your vehicle 13hp"

But anyway, usually the loss of torque isn't noticeable, but still, it's a loss. Add several losses one at a time and you may not notice the overall effect, but it could be significant.

 

I have a bosley chip that gives me read outs andwhen i got home i did a diag. and gave me 12.6 something moore HP...Ill try putting the results out.

 

You've got a what?

12 hp differences can be easily attributed to environmentals - temp, air pressure, humidity, tire pressure, weight, etc. G-tech's are cool for estimating things, but they're not accurate for actual measurements.

 

When you guys say that on a 5.9 you would put three inch singe you mean run a single exhaust instead of dual??? and would you recomment putting an h or an x pipe on the dual??

 

I'd run a single 3", but that's just me. Years ago when I was looking into it I read an article that found a single 3" for a mostly stock 5.9 was about the optimum setup for a driver. Drag racing, sure, go bigger. But for a street vehicle, the single 3" was about right.

If you do go duals, definately get a crossover pipe. X or H, either one. It's needed to equalize pressure between the sides. From the 5.0 world I think the H sounds better but the X makes slightly better power, but I could be remembering that incorrectly.

Keep in mind that my trucks get used hard for towing race cars around and screwing around on trails - I need my low end grunt.