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rcolburn
PostPosted: Wed Feb 20, 2008 4:37 pm 
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3 Deuce Weber
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Joined: Thu Apr 08, 2004 1:33 pm
Posts: 62
Location: Maine
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I recently got my front Dutra Dual from Doug and am looking forward to putting in a dual exhaust when it stops snowing (I'm in Maine you see...). I've read a bunch of posts about the optimal exhaust pipe diameter, but am a little confused about how it can effect performance. I don't have a lot of cash to throw at a fancy custom set of pipes and was looking at a kit from Jegs > http://www.jegs.com/i/JEGS/555/30500/10 ... 68%7C10253 < that might only require my exhaust shop to do some custom work to fit it to the dduals BUT it only comes in a 2.5" diameter. Would this be too big for a stock super six set up? If this has already been discussed at length and I missed it, I'd be happy with a link to the thread, otherwise any advice would be appreciated.

Cheers,

RC in ME
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Evilsizer
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PostPosted: Wed Feb 20, 2008 5:24 pm 
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TBI Slant 6
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Joined: Wed Feb 13, 2008 3:12 pm
Posts: 122
Location: Austin, Texas
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according to this thread here
http://www.slantsix.org/forum/viewtopic.php?t=26833
Quote:
Those Hooker's would work well, BUT may not fit with some of your mods?

The Clifford Street Rod headers work well and fit well. Not the best possible design, but they've worked well for me. Here is my recommendation:

- Cliff headers
- buy a bona fide Flowmaster or similar Y-pipe with 2.25" inputs and 3" output
- run 2.25" pipes out of the engine bay down to 1" to 4" behind the trans X-member, then into Y-pipe
- 3" from Y-pipe back to muffler in front of rear axle
- Super Turbo or similar 3" ID muffler
- 2.5" or 3" from muffler back
- optional - short glass pack or resonator near back bumper to quiet everything down.

If you want to keep your present 2.5" exhaust (not recommended based on track times), get a 2"X2.5" Y-pipe at same position and run 2" pipes from headers to Y.

Lou

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Joshie225
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PostPosted: Wed Feb 20, 2008 5:24 pm 
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Supercharged
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Joined: Thu Jan 27, 2005 8:32 pm
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Location: Portland-ish
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Unless you really want the sound of duals you're better off from the standpoints of power, weight and cost to use single exhaust. 2 1/2" single exhaust is really more than you need. This has been previously discussed at length.

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terrylittlejohn
 Post subject: exhaust
PostPosted: Wed Feb 20, 2008 6:02 pm 
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Turbo EFI

Joined: Tue May 17, 2005 4:26 pm
Posts: 1237
Location: CBS Newfoundland Canada
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if the jegs link is right you are looking at dual header kit, with your dutra duals a 2in dia y pipe 36in long joining into 2 1/2in single pipe to the muffler and out to the bumper or rear tire what ever is your preference will be the best, just make sure the muffler shop makes a true y joint were the two head pipes meet and goes to 2 1/2in pipe 8)
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vynn3
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PostPosted: Thu Feb 21, 2008 7:07 am 
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Turbo EFI
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Joined: Fri Jul 16, 2004 5:22 am
Posts: 1134
Location: Carrollton, TX
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My understanding is that exhaust diameter affects the torque curve, moving it up and down the rpm range. The bigger the pipe, the further up the torque curve. But since our little slants typically only rev to 4-4500K, I think TWO 2.5" pipes would push the torque curve beyond the usable range.

I have Dutra manifolds into dual 2" pipes right now, and I thought THEY might be too big. I'm very satisfied with the all around power and torque. I think you'll find that the labor intensive part of the exhaust work is in the first few feet of pipe anyway, from the manifolds to the tranny crossmember — I doubt it would cost too much more to run the exhaust the rest of the way to the back or the car.

Good luck and keep us posted!

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rcolburn
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PostPosted: Thu Feb 21, 2008 8:33 am 
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3 Deuce Weber
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Joined: Thu Apr 08, 2004 1:33 pm
Posts: 62
Location: Maine
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Thanks for the links and tips. I figured from what I had read 2.5" would be too big. We'll see what the quote for the full set from my shop is and when spring comes I'll get some pics of whatever solution works out.

RC
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