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#1 |
Registered User
Join Date: Jul 2012
Location: McMinnville, OR
Posts: 80
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3 inch exhaust
Anyone running 3 inch exhaust coming out before the rear tires? I'm getting my exhaust done on Wednesday and that's how I am getting it. Anyone have any input or any pics?
Thanks!
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1969 CST/20 396/TH400 Tach Posi |
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#2 |
Registered User
Join Date: Jul 2013
Location: Prescott Arizona
Posts: 343
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Re: 3 inch exhaust
2-1/2" with 4" stainless tips. Cheap $39.00 each Thrush (Flow-master rip-offs) sounds quiet, low rumble at idle, sounds great under power, no annoying cruise drone either. YES a quality X-pipe is superior, but couldn't fit one without possibly cooking the front u-joint and facing crazy bend issues, This simply balances the cylinder banks and still sounds damn good, again cheap versus $100.00 X-pipe too.
My opinion, I'm an old fart ex-racer, and can tell you 2-1/2 is good for up to 600 HP and any flow advantage with 3" is seen at high RPMs, so doesn't make sense to me to design for 5% of time performance in a street truck, in limited space but, to each his own, eh? My Two Cents, hope it helps
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68 GMC SWB Vortec 5.3 98 Chevy Blazer ZR2 94 Mazda Miata, LS2 6 speed, sold "No matter what happens, nobody gets out alive" Last edited by Lees68GMC; 04-14-2014 at 07:53 PM. |
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#3 |
Registered User
Join Date: Jul 2009
Location: Space Coast, Fl.
Posts: 1,050
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Re: 3 inch exhaust
Lees68GMC, nice clean installation... are you the welder?
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Dad always said, "Son, WISH IN ONE HAND, and ......." -------------------------------------- -------------------------------------- Current toy trucks: '71 GMC 1500 SUPER CUSTOM short/step, orig. dk. blue, 350/700r, ps,pb, A/C '72 Blazer 2wd, ochre & white, 454, tremecTKO 500 5spd. ps, pb, A/C, tilt Last 10yrs of hobby vehicles, had a FEW more in the 50yrs. before these: '66 Plymouth Belvedere City of Miami cop car clone. '70 Nova 406"sb, 13.5-1, solid roller, Brodix, p.glide/t.brake, back halved, 9" Ford, spool 4.88, cage,ladder bar/coilover, 10.5 tire....... SOLD!! '67 C10 short/step side mount spare -- SOLD!! '72 Jimmy 2wd, 350/350, ps, pb, fun driver, lots of bondo & a shiny red paint job..... SOLD!! '69 Nova 350, 4spd, A/C, ps, p.b, ...SOLD!! |
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#4 |
Registered User
Join Date: Jul 2013
Location: Prescott Arizona
Posts: 343
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Re: 3 inch exhaust
I wish, no local friend did it, I just said how and where I wanted it run.
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68 GMC SWB Vortec 5.3 98 Chevy Blazer ZR2 94 Mazda Miata, LS2 6 speed, sold "No matter what happens, nobody gets out alive" |
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#5 |
Registered User
Join Date: Nov 2000
Location: Huntsville Ontario Canada
Posts: 4,052
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Re: 3 inch exhaust
I had my truck like that for a few months......dual 3" with super 40's. then I added the H pipe.....then tail pipes out the back made it better but it was still draining to drive. I couldn't take the noise. I am not a old guy either. depends how often/far you plan on taking the truck out.
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1968 Suburban numbers matching all original truck now equipped with 6.0/4L80 on Accuair http://67-72chevytrucks.com/vboard/s...d.php?t=625017 1967 C/20 6.0/4L80 Roofing Truck 1990 V2500 Suburban "Plow Truck" 2005 TAHOE DD |
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#6 |
Registered User
Join Date: Nov 2000
Location: Huntsville Ontario Canada
Posts: 4,052
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Re: 3 inch exhaust
..
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1968 Suburban numbers matching all original truck now equipped with 6.0/4L80 on Accuair http://67-72chevytrucks.com/vboard/s...d.php?t=625017 1967 C/20 6.0/4L80 Roofing Truck 1990 V2500 Suburban "Plow Truck" 2005 TAHOE DD |
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#7 |
Registered User
Join Date: Sep 2012
Location: Layton, Utah
Posts: 186
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Re: 3 inch exhaust
Subscribed. Had similar question
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James B. 1967 Chevy Fleetside Shortbed 4X2 (Black & Beautiful) 1971 Chevy Fleetside Shortbed 4X4 (White & Rough) |
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#8 |
Parts and more parts
Join Date: Nov 2003
Location: Lebo, Kansas (middle of nowhere
Posts: 6,821
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Re: 3 inch exhaust
I agree with the comment about the capacity of the 2 1/2" piping. The 3" piping may and in many cases will provide a loss of efficiency in the exhaust system. The larger tubing will provide for a loss of scavenging effect on the engine and in the long run, cost you horsepower and possibly fuel economy. The removal of exhaust is important, all the way back to the intake process, since the removal creates the vacuum that really pulls the new fuel laden air into the cylinder. If the exhaust gases are allowed to travel lazily out the rear, then the pulling effect is lost. The right size piping will allow the exhaust to cool and collapse the full length of the piping giving that vacuum effect and not a reversionary effect that will cause the engine to perform poorly.
Looking great is not always the right answer. I spent a lot of time on a phone, talking to engineers for Flowmaster and Magnaflow, when I built my exhaust for my GMC.
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Frank |
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#9 |
Senior Member
![]() Join Date: Mar 2003
Location: Colfax-California
Posts: 8,553
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Re: 3 inch exhaust
A single 3'' pipe behind the rear wheels will flow anything you can throw at it, unless you're putting in a big block with a blower that's gonna spin above 6k
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#10 |
Registered User
Join Date: Dec 2011
Location: winnipeg
Posts: 1,107
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Re: 3 inch exhaust
Exactly,I know guys who run well into the 450hp range with a single 3 inch system. 2.5 is plenty in dual form.
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#11 |
Senior Member
Join Date: Jan 2003
Location: daytonabeach
Posts: 22,956
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Re: 3 inch exhaust
3" exhaust is the hot tip for makin noise and not goin anywhere fast
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71c-10 350/2004r/4:11 lowered3/4 longbed/dead by hurricane MEANING OF DEATH::::: SOMEBODY ELSE GETS YOUR STUFF DONT BELIEVE EVERYTHING YOU THINK TAKE MY ADVISE;I DON'T USE IT ANYWAY |
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#12 |
Registered User
Join Date: Apr 2011
Location: formerly NY currentlyNC
Posts: 390
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Re: 3 inch exhaust
had mine in front of the wheels with a shortbed and a sliding rear window (no A/C )....after 2 hrs of driving the fumes would damn near kill me
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1970 short step c10 leaf spring 454 |
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#13 |
Junior Member
Join Date: Dec 2001
Location: Bethel Park, PA USA
Posts: 127
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Re: 3 inch exhaust
Question for Lees68GMC. I noticed you ran your exhaust through the trailing arm cross member. My LWB C-20 has a brace on each side of the X-member going to the frame. Did you eliminate them, or does you truck not have them? Also, did you just weld a larger piece of pipe into the X-member to run the pipe through?
Great looking exhaust!
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67 C-20 LWB 56 Nomad--- nope, sold it ![]() 75 Stingray 13 Silverado crew cab 08 Trailblazer (wife's) ![]() Pittsburgh, PA |
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#14 |
Registered User
![]() Join Date: Jul 2012
Location: White Salmon, WA
Posts: 263
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Re: 3 inch exhaust
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#15 | |
Account Suspended
Join Date: Jan 2007
Location: Tucson
Posts: 2,183
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Re: 3 inch exhaust
Quote:
2.5 inch is more than adequate for anything you can put in that truck and you will leave the shop with a heavier wallet. You can always add 3 in tips. I ran 2.5 in straight out the back with the dumps exiting under the steps. |
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#16 |
Senior Member
![]() Join Date: Sep 2007
Location: Albuquerque NM
Posts: 7,848
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Re: 3 inch exhaust
I actually run 2 1/4" with ramhorns and super 40s flowmasters and i have no issues at all. Sounds good and i Dont get tired of the rumble while dring. I gotta add a h pipe though
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1967custom |
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#17 |
Registered User
Join Date: Jun 2011
Location: United States
Posts: 158
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Re: 3 inch exhaust
I'm running 2 1/2-inch stainless on my '68 behind a supercharged LS327. Put out 500hp to the rear wheels on the chassis dyno so 3-inch isn't necessary.
The whole install is here. Good luck! |
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