Ethan91

Here in the next couple weeks I should hopefully be starting on my build. I'll be swapping in an LS3 6.2L. I had originally planned on running true duals, no cats, and flowmaster 40's using 2.5" pipe. A few guys on the site told me it would be much easier and cheaper to run a single 3.5" or an 4" pipe with no cat and the same muffler and I should see the same results if not a little better? What do you guys think about this?

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tom86iroc

a mufflex exhaust would be easier to put in then true dual IMO i'm goin mufflex this winter witha 4inch kit dual is so tough on our cars because of room with the drive shaft and torque arm not to mention the way the floor is formed some people have done it but it costs a fortune over a 4inch kit

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Shift06

Is your motor actually 700RWHP? If so might wanna go bigger lol. I didn't see that part in the swap forums. 2.5 duals won't be very good for 700 RWHP.

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'91 GTA WS6 | '99 LS1 / 4L60E | Ported 853's | Comp Custom Grind 224/224 @ 117 LSA | Patriot Dual Springs w/ Titanium Retainers | Comp 7.350" Hardened Pushrods | Ported TB | Walbro GSS340 | Prof. Products AFPR (Coming along nicely )

Ethan91

haha no. The transmission is rated for 700rwhp. I plan on pushing somewhere around 500hp at the flywheel.

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InfernalVortex

You can do duals if you get a T56 and a custom-made crossmember. You'll have some decent ground clearance that way.

But you'd still get better ground clearance by running a single.

Here's my single 3.5:



I'd suggest getting it run over the axle if you want to lower the car. But if you are fine with stock ride height, you've got plenty of room to tuck a muffler back there.

Unless you run over something larger than a 2 liter bottle, you're good to go:




But if you're gonna use the 4l60e, you're gonna need to go with shorties to get decent ground clearance near the front of the car, so you may as well just stay with a 3.5 single to begin with.

This was how my dual 3inch setup was:



There's only so much space between the crossmember and the ground... and you can tuck up that 3 inch pipe as high as you can, but it's stil gonna take up 3 inches of space.


Also cross sectional area comparison:

single 2.5 inch pipe = 4.9 sq inches
dual 2.5 inch pipe = 9.8 sq inches

single 3 inch pipe = 7 sq inches
dual 3 inch pipe = 14 sq inches

single 3.5 inch pipe = 9.6 sq inches

single 4 inch pipe = 12.5 sq inches


That may help you a bit. A single 3.5 is about the same as a dual 2.5

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Thridgen60

I made a 3in into 4in y-pipe off of my hawks headers. I have a 4" electric cutout under the rear seat and then i reduced it back to 3" to go over the axle and to my flowmaster. I absolutly love this setup, i love driving around with the cutout open but then you can still close it if you have to pass a cop or something. I am running a cammed 6.0L with L92s so it is around 500 flywheel and a 700r4 trans.

mikesanto70

so a single 3.5" or 4" would flow better/make more power than a dual 2.5" on a cammed LS3, cause i really dont car about looks, I just want functionality and clearence because I plan on lowering it 1.5 to 2" as well for handling and 190mph top speed runs

PURPLEFORMULA

You will get better flow and more HP with true duals with a cross over (X or H pattern). I have 2 1/4" with the same clearance as stock, you just have find someone that can do a total custom job. Also get BMR's upper panhand relocation kit and you can easily fit dual 3". More total flow is better, 5" total flow is better than 4" or 3.5".

Eric

Thridgen60

Here is a great link. Just go down to the exhuast section of it.

http://www.ls1tech.com/forums/genera...heads-cam.html

This guy said with a 3in in 4in y-pipe he loss 1hp and gained 10 rwtq vs. 20in collector extensions. IMO 3in to 4in or 3in to 3.5in is the only way to go.