2 1/2" or 3"

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racerx

racerx

racerx
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northwest nj
Looking for input on exhaust size. 71 Duster 4-sp, 496 stroker with tti headers. What are the pros and cons. Car will be street/strip, no cage so have to stay above 11.50 for now so not looking for maximum output from this motor. Are there clearance issues with the 3" system? Oh, I plan to use the tti x-pipe system. Don't want a tinny sound. Muffler recommendations? Thanks FABO
 
I have tti fenderwall headers with 3" pipes and an h-pipe with hooker aero chambers. I think they are offset inlet and centered exhaust, with dumps just in front of the axle. I've been happy with the sound, everything fits just fine underneath and have received many compliments on the sound. Its behind a built 440.
 
Without knowing the power output of the engine, 3 inch is what I'll go for. Considering the size of the engine. I've seen pictures of 3 inch exhaust on here before. IDk about any MOD if need be though. Sorry.
 
Go for the 3" w/ Dynomax Ultra Flows. 3" will not clear relocated leaf springs with a stock fuel tank. A fuel cell is required if exhaust is run to the bumper. 496 stroker usually means in excess of 500 hp.That's supposed to be the dividing line from 2.5" to 3". Hell, I'm putting 3" on my 408 stroker & I don't have 500hp. At least not yet!
 
I haver 2.5 on mine.2 inch primary tubes ,3.5 inch collectors necked down in front of the h pipe. I will uncap it to race.
 
had 3" on my small block..

used these mufflers...

DSC06161.JPG



this x-pipe from magnaflow

exhaust%20006.jpg



it fit fine. my springs were in stock location with a stock gas tank..

exhaust%20010.jpg




here is how it sounded. it isn't as loud as it sounds in the video and is quite a bit deeper sounding then in the video..

http://www.abodyjoe.com/pictures/71 Dart/exhaust/dart exhaust.avi



i now have 3" to the mufflers and 2 1/2" tail pipes because the 3" didn't fit with the triangulated 4 link.
 
i put 3" with an X pipe on my mild driver 360 if that tells you anything. i always like to run the collector size if i can. 3" fits pretty good on a A body. now the 4" on my dart is a different story....
 
The theory is; after the gases leave the head, and get 6" out, then there not that much back-pressure, as the engine want's some back-pressure.
This ought to stir up opinions, lol.
 
Like stated before: 500hp is the cut-off for 2 1/2" exhaust so go with the 3". I like the set up that "abodyjoe". very clean and tidy.

I have never been a fan of DynoMax mufflers. I have a set on a truck once. They rusted out around both inlet/outlet pipes. There was no other rust on the mufflers anywhere else and they weren't that old.
 
id go 3", i just built a new 3" system for my dart. made a 3 1/2" x pipe to match the collectors, reduced it to 3" before the mufflers dynomx ultraflows and a twister muffler on the tailpipe hopefully keep it sort of quiet inside. ive seen plenty of cars with the tti 3" systems they fit real nice but expensive. i like to build my own. im not sure what size im going to go on my duster with the 400.
 
green1 said:
The theory is; after the gases leave the head, and get 6" out, then there not that much back-pressure, as the engine want's some back-pressure.
This ought to stir up opinions, lol.
Click to expand...
I tend to agree with the backpressure theory.i had a 340 valiant that ran better with the exhaust on than with open headers. i guess the engine was trying to tell me something. bigger is not allways better.
 
Al right then .lets ask this question Im running a mildly bulit 360 that is roughly 400 hp. TTI headers and 3" TTI exhaust sytem. Is this actually to big for my output.
 
green1 said:
the exhaust port, from the head, only cares about the first 6 ".
Click to expand...

Oh yeah then in that case, he can just run headers with 1 7/8" single exhaust pipe to save money. Dumbest **** I ever read.
 
green1 said:
The theory is; after the gases leave the head, and get 6" out, then there not that much back-pressure, as the engine want's some back-pressure.
This ought to stir up opinions, lol.
Click to expand...


yea right.... every car i've ever owned goes faster has responded to bigger exhaust.

i run straight 4" on my dart into 2 chamber flowmasters with no tail pipes (you wouldn't think that would create backpressure). pull it off the car instantly picks up a tenth & 1/2.

my challenger with a basically stock 360 in it (13 sec car) picked up 3 tenths when i chopped the 2 1/4 tail pipes off.

440 in my belvedere, ran 12.20's with 3 in exhaust no tail pipes. stepped up to 3 1/2" and the car went 11.90's.

that back pressure theory is absolute crap if you have your car jetted properly. using exhaust for proper scavenging is a different story.
 
68 HEMI GTS said:
that back pressure theory is absolute crap if you have your car jetted properly. using exhaust for proper scavenging is a different story.
Click to expand...

i have to agree. i had 3" to the bumper on my dart and when i had it running the best i could to my tuning abilites, had good free flowing mufflers with an X pipe. i pulled the exhaust off and tried rejetting it. and it didnt pick up anything. at all. i had a brain storm and thought i was going to detune it and built a 3" into 2 1/2" system with ultra flows and that alone killed it. i think the 3" exhaust was damn close to no restriction and if anything the 1 3/4 headers kept it from gaining when i pulled the exhaust off. it was way too loud inside for me to ever want to try it again. if you are ever going to look for the msot power you possibly can have with the pedal to the floor, your goign to want to go with 3" over the 2 1/2". if you dont think you will ever be in that situation :bs: , then go with the 2 1/2".
 
I'd like to see a real world chassis dyno & drag strip test results from 2.5" exhaust to 3".
 
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