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Old 07-11-2007, 06:53 PM
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Exhaust 3" vs 2.5"??

I have a chevy 383 that will make 450hp to the crank and i plan on running a 150hp shot of nos later. This will be a dual system for my 78 camaro.
What size exhaust pipe should i run???
Will i lose tq with 3"?? or is 2.5 to resictive??
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Old 07-11-2007, 07:21 PM
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You should be just fine with dual 2 1/2" pipes.
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Old 07-11-2007, 09:43 PM
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Dual 2.5" pipe is good for 440-450hp, but the mufflers may be another story.
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Old 07-11-2007, 09:43 PM
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ditto ^^^ I agree
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Old 07-12-2007, 11:47 AM
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What about if i run a 150 shot of nos to it??

Will i lose power or trq with 3"???

I plan on running the new flowmaster supper 44s.
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Old 07-12-2007, 10:10 PM
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I'd probably go with the 3", if you're really making that much power. You won't necessarily lose torque if you use it, but you may have to recalibrate your carb some to compensate for the extra air flow.
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Old 07-13-2007, 06:36 AM
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I agree with Jim. As well, mufflers will make a difference too. Use a mandral bent system with a straight through muffler design such as the Dyno Max Ultra flow. Mandral kits are no more money that a muffler shop kink job. You also leave room for more improvements. You might want to consider 1 3/4" headers too if your not already using them. I use a 3" mandral with 1 3/4" headers with the ultra flows. The system is quite around town, sounds great at full pop. This is on a 475 hp 406.
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Old 07-13-2007, 08:15 AM
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flowmasters don't flow very well. They just have a very good marketing name.

Hooker Aero-chambers flow 50% better than flowmasters and aren't as loud.

Hook Aero-chamber Max Flow's will flow like a straight pipe and are about as loud as a flowmaster.

http://www.broaderperformance.com/mu...flow_tests.htm

2.5 pipe is good for 450hp (in theory). 3.0 inch might be a better choice with n20. I ran 2.5 inch with a 450hp engine with 200 shot n20 and it ran ok. But never tried 3 inch.

Yes, use mandrel bent pipe. I buy J-bends from summit and make my own exhaust.
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Old 07-13-2007, 08:33 AM
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Quote:
Originally Posted by 89SDime
What about if i run a 150 shot of nos to it??

Will i lose power or trq with 3"???

I plan on running the new flowmaster supper 44s.
Header sizing and length is where your power is.

All you want the exhaust system to do is get the gases out with minumum backpressure. Put a 3" dual system in with a X pipe and that will be the least restrictive. You'll likely make more torque. On the bottle the engine will like this MUCH better.

Spec your mufflers based on the amount of noise you want to make. Over the past 20+ years I have not seen any real world testing showing much more than a 10th of a second difference in muffler brands (within their specific classifications) in the quarter.
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Old 07-13-2007, 08:38 AM
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I have a 78 Z28 with a fairly healthy 355 roller on small shot of nitrous.

I run a full mandrel bent 2.5" exhaust with a set of 2 chamber slowmasters.

I loose between 2-3 tenths in the quarter going from open headers with extended collector to the exhaust. 10.70's to 10.90-99's.

If your looking for a setup... I actually have mine for sale. :-)

edit... thats running 1 3/4 primary headers

Last edited by bigbadbowtie; 07-13-2007 at 08:51 AM.
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Old 07-13-2007, 02:06 PM
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real world muffler testing


http://www.boyleworks.com/ta400/psp/exhaust.html
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