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02-29-2012, 10:10 PM
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#1 |
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Registered User
Join Date: Jul 2010
Location: Calgary, Alberta
Posts: 19
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3" exhaust
Anyone running 3" exhaust all the way to the back of their truck? Magnaflow only makes a 2 1/2" kit but I have a fairly serious 454 (500-550hp) or so maybe a bit more and was thinking 3" would be better? My truck(71 GMC short box) has leafs. Can I get tailpipes to fit in 3"? Any thoughts would be great. Or should I be ok with the 2 1/2?
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02-29-2012, 10:16 PM
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#2 |
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Registered User
Join Date: Jul 2011
Location: Des Moines, Iowa
Posts: 3,016
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Re: 3" exhaust
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project: "my happy mess" |
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03-01-2012, 12:30 AM
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#3 | |
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The Engine Whisperer
Join Date: Sep 2006
Location: Ohio
Posts: 770
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Re: 3" exhaust
Quote:
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03-01-2012, 12:41 AM
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#4 |
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Senior Member
 
Join Date: Feb 2001
Location: New Madison, Ohio
Posts: 21,373
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Re: 3" exhaust
I have 2 1/2" on my 402BB and it sings a fine song.
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A husband can be right...or...A husband can be happy.  67-72 Chevy and GMC Trucks...The Classic Truck for the Classic Folk.  1970 CST Two tone green, 402BB, 400 Automatic, Tach, Buckets, AC, AM-FM, Tilt, GM CB, GM 8 Tract, LWB, etc   JOHN 17:3...The better side of "LIFE" Remember: Everyday is a good day...Some are just gooder! |
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03-01-2012, 12:44 AM
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#5 |
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Registered User
Join Date: Jul 2011
Location: Des Moines, Iowa
Posts: 3,016
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Re: 3" exhaust
Agree. The chart above suggests 2 1/2" to 3" for 250-550 HP. You should be "ok" with 2 1/2".
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project: "my happy mess" |
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03-01-2012, 12:51 AM
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#6 |
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Registered User
Join Date: Jul 2010
Location: Calgary, Alberta
Posts: 19
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Re: 3" exhaust
I just wasnt sure and got different answers from a few people. The engine is a 476ci tall deck with 10-1 comp, ported 781s with 2.25/1.88 valves and a solid roller(646/653lift 242/248@050) performer RPM air gap and a 850 holley. Oh and a 150 shot of juice if im feeling brave. lol. And the HP was just a guess. Not been dynoed yet so may be way off.
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03-01-2012, 07:54 AM
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#7 |
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Special Order
 
Join Date: Nov 2004
Location: Mt Airy, MD
Posts: 85,851
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Re: 3" exhaust
That chart is inaccurate,IMO. The benefit of 3" exhaust kicks in at 500+hp and below that I feel performance is not as good as with 2 1/2. I'd probably go to 3" somewhere between 600 and 700hp
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03-01-2012, 09:24 AM
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#8 |
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Senior Member
Join Date: Jan 2003
Location: daytonabeach
Posts: 22,956
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Re: 3" exhaust
there might b a little increase in high end full throttle bonsai horsepower but a noticable loss of street friendly loend around town torque
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03-01-2012, 09:56 AM
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#9 |
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My Carbon Footprint
Join Date: Oct 2008
Location: Orygun
Posts: 5,527
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Re: 3" exhaust
I think it's harder to route around the coil rear end as apposed to the leafs.
Keep in mind that it's just as important to correctly pick your header tube diameter as it is your exhaust dia. The size of tubing can move your power range up or down. In these areas, I always like call 2 or 3 different big name exhaust companies and see what they have to say. I bet 2 or 3 will say 2.5 is fine. |
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03-01-2012, 11:23 AM
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#10 | |
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Registered User
Join Date: Jul 2011
Location: Des Moines, Iowa
Posts: 3,016
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Re: 3" exhaust
Quote:
Don't get me wrong (it's early and I need coffee), I get what you're saying, 2 1/2" is plenty enough for most.
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project: "my happy mess" Last edited by litew8; 03-01-2012 at 11:32 AM. |
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03-01-2012, 04:40 PM
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#11 |
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Cool Truck
Join Date: Dec 2008
Location: Bowie,MD
Posts: 1,869
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Re: 3" exhaust
My truck has 3 inch exhaust on it, but that was done before I bought it. It is just a mild 292.
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