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Old 06-09-2019, 07:43 PM
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Default Replacing 2-1/2" system w. 3" ... is it worth it?

I had a mandrel bent 2-1/2" system with H pipe and Goerlich Accelerator mufflers done 2 years ago. I was thinking I would enjoy the lower db of the mufflers and H pipe. Now I am regretting it and want to go back to the chamber Thrush mufflers I used to run and take out the H pipe. The car lost that "cammy" idle sound it used to have without the H pipe.

The Goerlich's are longer cases so I am probably going to have to have new mid-pipes fabricated anyway to avoid looking like a patched together mess underneath and so am considering just hanging a complete 3" system under it and being done with it. Local muffler shop charges $125 for complete R&R and a system from summit is around $300.

My 2-1/2 system with the Thrush chambered mufflers was pretty wicked sounding. How much louder/obnoxious will a 3" system be as compared to the 2-1/2"? Should I expect any performance gains out of +/- 400HP 455?

Let me know your experiences with this kind of upgrade.

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Old 06-09-2019, 09:48 PM
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I don't think you will see any performance gain with a 3" exhaust at your power level. You need to be above 550 Hp for a 3"system so it will be a matter of sound what you choose.

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Old 06-09-2019, 10:30 PM
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I picked up 2/10’s plus by switching from 2 1/2 to 3 inch exhaust off on my 2 1/2 RamAir manifolds. Both exhaust systems were mandrel bent with x-pipe , dual mufflers and tail pipes . My motor is approximately 450 HP

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12.075 @ 112.70
12.092 @ 112.43
12.128 @ 111.71

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Old 06-10-2019, 08:31 AM
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Quote:
Originally Posted by form74 View Post
I picked up 2/10’s plus by switching from 2 1/2 to 3 inch exhaust off on my 2 1/2 RamAir manifolds. Both exhaust systems were mandrel bent with x-pipe , dual mufflers and tail pipes . My motor is approximately 450 HP
Did you make any other changes??

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Old 06-10-2019, 09:44 AM
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I picked up the 3" summit kit with mufflers for my '72 Camaro. If it's loud/nasty you're looking for, this is where it's at. I haven't taken it out for a longer drive yet so I can't really say about drone or anything. I went from a 3 1/2" glasspack that exited just in front of the back tires, so I actually quieted things down a bit.

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Old 06-10-2019, 11:04 AM
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Quote:
Originally Posted by gs462 View Post
Did you make any other changes??
I changed out the front 15x7 Rally II's with 255/60-15's with 15x6 with 205/75/15'.

Nothing Else, I will post some Time Slips tonight or tommorrow when I'm at home.

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74 Formula
469, 6X-4's, 72 Intake, Ramair Manifolds.
3 inch exhaust with x-pipe
Custom Roller Cam, 1.52 Roller Rockers
Quadrajet done by Cliff
3:42 gears


12.075 @ 112.70
12.092 @ 112.43
12.128 @ 111.71

  #7  
Old 06-10-2019, 11:13 AM
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With all these different brands of chambered mufflers...............are they any different in sound that a typical Flowmaster mufflers? I' had a pair of Super 44's (3" with X-pipe))on my t/a with healthy cam and really didn't care for the tone, kind of docile compared to Flowmaster 40's and H-pipe on my old SD455 with HO-Racing cam.

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Old 06-10-2019, 11:45 AM
Steve C. Steve C. is offline
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MANY years ago I put on Flowmaster mufflers, to me personally they had a 'tiny' sound I did not care for. Although not a chambered design since then I've only used DynoMax Ultra Flo Welded or the Super Turbo and never looked back. That said, everyone has personal preference.

Related- a "H-pipe" crossover and "X-pipe" crossover sound much different.

http://www.dynomax.com/mufflers


.

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Last edited by Steve C.; 06-10-2019 at 11:53 AM.
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Old 06-10-2019, 12:05 PM
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There are different videos out there comparing different brands. But often they may not be apple-to-apples testing since some changes may have been made. Like adding a X-pipe with the change. Or going from 2-1/2" exhaust to 3" with the change.

Here is one Flowmaster vs Dynomax video........

https://www.youtube.com/watch?v=0o3QTdNYLBw


.

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'70 TA / 505 cid / same engine but revised ( previous best 10.63 at 127.05 )
Old information here:
http://www.hotrod.com/articles/0712p...tiac-trans-am/

Sponsor of the world's fastest Pontiac powered Ford Fairmont (engine)
5.14 at 140 mph (1/8 mile) , true 10.5 tire, stock type suspension
https://www.youtube.com/watch?v=qDoJnIP3HgE
  #10  
Old 06-10-2019, 12:53 PM
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I'm a dynomax fan, as they have produced much less drone issue and a more refined sound in everything I've used them on.

Even with that said I still have one car with flowmaster super 40's.

As for exhaust pipe size comparisons, I did that very thing on my chevelle many years back.

Started with a complete 2 1/2" flowmaster kit, with an "H" cross over and mandrel bends and flowmaster mufflers with Flowmaster 2 1/2" tail pipes. Car was stuck in the 12-teens at 112 mph.

I switched to a 3" system, with a Dr. Gas "X", still Flowmasters but in 3", and 3" torque tech tailpipes. Basically a 1/2" larger system. Right off the bat with no other changes it clicked off 11.70's at 116 mph and I eventually widdled that down to mid 11's at 118 mph and that's pretty much how the car still sits today.

Sometime I would like to install some dynomax mufflers on the car if I ever get around to it just because I prefer the more mellow sound of them, and if I want to make noise or simply bypass the whole system at the track I'll just open the electric cutouts.

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Old 06-11-2019, 12:03 AM
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2.5" pipes into 3" Flowmasters, into 2.25" tailpipes

vs.

3" pipes with H, into 3" Borla ProXS, into 3" mandrel tailpipes.

7.8:1 455, unported heads, Tri-Y headers, Performer intake, Q-jet (metering rods changed to optimize both configurations), custom low-lift 222/242 116lsa cam.
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