is a 3" exahust too big?

coolblue65 · Oct 1, 2007

Like the subject says, is a 3" exahust pipe diameter too big? Reason I am asking is that currently I have an old rusted 2.25" system with no x or h-pipe, and flowmaster mufflers that I have been looking to upgrade, especially since I put in the DSS 347 which should be a solid 430 HP (+/-15).

The standard kit choices are 2.5" tubing, but there are a couple that you can get 3", I know the 3" will be louder but I am not sure how much (not too concerned about noise though) and I know the larger 3" will probably cost me a some low end ponies, but is it negligible? because I am assuming I will gain plenty up top by not having the 2.25" tubing, and traction down low is already an issue.

thanks

D.Hearne · Oct 1, 2007

2.5" is plenty.

10secgoal · Oct 1, 2007

D.Hearne said:
2.5" is plenty.

Agreed. I lost a tenth in the 1/8 on motor when I went to 3in with the old setup.

xoxbxfx · Oct 1, 2007

68GT500KR_Vert · Oct 1, 2007

for you YES; I need it because I have a 550HP Big Block.

CraigMBA · Oct 2, 2007

3" will be almost twice as loud as 2 1/2.

You say you won't care but you will.

Vinyl66 · Oct 2, 2007

Go with mandrel bent 2.5". I was contemplating the same change a while back on my 347 that is built very much like yours. I was swayed away from the 3" by people that have it saying that it is MUCH louder than the 2.5" pipes.
Plus, your cam is the roller version of my XE274H so you will not be seeing the high side of 6500 rpm anyway.

FWIW: I have run 11's in my 347 with slightly lower compression than yours, smaller carb, same intake, flat XE274 to your roller, and same gears. All through 21/2" h pipe, flowmasters, and 2 1/2" tailpipes.

chromedog · Oct 2, 2007

my main issue with anything over 2 1/2 (besides noise) is the clearance between the drivers side leaf spring, and gas tank... i have 2 1/2, and even that is tight.

GNN60GT500 · Oct 2, 2007

2.5" for sure- I work for MagnaFlow and have the 2.5" kits on all 3 of my Stangs that are within the same hp range as yours-

If you were making closer to 500hp, then I would say to start looking at the 3" kit-

coolblue65 · Oct 2, 2007

OK its unanimous, thanks everyone, makes that decision easy.

Vinyl66- did you run mid 11's on street tires or on some form of radial/drag tire? My goal is low 12s on street tires and 11s on drag tire. Hoping to make it to the track in the next few weeks.

GNN60GT500- do you have any sound clips of your Mustangs? I have not heard a Magnaflow system in person and would like to.

chromedog · Oct 2, 2007

you wont be sorry with the magnaflows... go to their website, as they have soundbites of various cars. i REALLY like the sound of mine (hedman shorties, mandril bent, with x pipe, through 2 1/2" tailpipes)

67staaang · Oct 2, 2007

sorry to hijack the thread but would you guys rather have x pipes or h pipes?

D.Hearne · Oct 2, 2007

X pipe or what I built for my 89 V8 Ranger--- this is a single 5"Dia. x 12" Long exhaust pipe, welded in twin 2.5" pipes in both ends to create an "equalizer chamber, in effect the twin 2.5's go in, then exit back to twin 2.5's then into the turbo mufflers. Sounds smooth and has a nice mellow tone. Full tail pipes out the rear.

coolblue65 · Oct 2, 2007

D.Hearne said:
this is a single 5"Dia. x 12" Long exhaust pipe, welded in twin 2.5" pipes in both ends to create an "equalizer chamber, in effect the twin 2.5's go in, then exit back to twin 2.5's then into the turbo mufflers. Sounds smooth and has a nice mellow tone. Full tail pipes out the rear.

Thats basically what my '92 vette has stock.

wicked93gs · Oct 2, 2007

considering a single 3" pipe can handle 400HP, then dual 3" is too big unless you plan on putting out in excess of 600HP

Vinyl66 · Oct 3, 2007

coolblue65:

I have never raced on my 245/45 street tires. And I really don't want to either. Too much feathering of the throttle and too much tire spin. I use 235/60/15 MT drag radials at the track. Even using those, I will still spin on the line if I hammer the throttle as opposed to quickly rolling onto the throttle.

Let us know how it performs at the track. Good luck and have fun!!

GNN60GT500 · Oct 3, 2007

coolblue65 said:
OK its unanimous, thanks everyone, makes that decision easy.

Vinyl66- did you run mid 11's on street tires or on some form of radial/drag tire? My goal is low 12s on street tires and 11s on drag tire. Hoping to make it to the track in the next few weeks.

GNN60GT500- do you have any sound clips of your Mustangs? I have not heard a Magnaflow system in person and would like to.

There is a sound clip of my 67 up on the website- but it wont be very accurate to you car as the motor in the 67 is a 428 with 11:1 compression-

http://www.magnaflow.com/04sound/04american.asp

(you have to go towards the bottom to find it)

I do have the system on a car with a 351W and a 302- and the car with the 302 sounds incredible- definitely the best sounding out of all 3 IMO- which is what your car would sound like with the 347-

For that car- wait until the next NASCAR race, crank up the volume- and thats what it will sound like-

is a 3" exahust too big?

coolblue65

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