Help with exaust size

69 Mach 393 · Jan 26, 2006

What size exaust should I useon my 69 Mach 1.What kind of cross over pipe do you like.
408 stroker
Roush heads
XE 274 comp cam
Victor JR intake
Holley Avenger 770 Vac Sec
Super Comp Headers 1 3/4" tubes
MSD Dist
6al box
Hydrolic Lifters
Roller rockers
FMX Automatic Trany
2800 Stall Converter
355 gears
9"Posi

0to100to0 · Jan 26, 2006

exhaust size....a heated debate

i would say "do a search" but i don't want to be that guy........
there is a 3" exhaust thread around here somewhere where everyone bashes someone for asking if he should use a 3" or a 3.5" pipe diameter......
they all said 2.5 is enouth and all that.....

i say: check out flowmasters website....they have a chart for horsepower and exhaust size.......check out magnaflow's website......they have a chart for engine displacement and exhaust size...all this info, i believe, is for n/a engines

myself? glad us asked.....i am planning on a 460 with around 575hp, and have decided on 3"

hope this helps
matt

xoxbxfx · Jan 26, 2006

69 Mach 393 said:
What size exaust should I useon my 69 Mach 1.What kind of cross over pipe do you like.
408 stroker
Roush heads
XE 274 comp cam
Victor JR intake
Holley Avenger 770 Vac Sec
Super Comp Headers 1 3/4" tubes
MSD Dist
6al box
Hydrolic Lifters
Roller rockers
FMX Automatic Trany
2800 Stall Converter
355 gears
9"Posi

honestly you will be completely fine with 2.5" exhaust but you might as well go all the way 3". Good luck findign someone locally that does 3"... found 1 place in teh DFW area that could do it for a decent price. A hpipe dumped in front of the rear axle cost me $350

dennis112 · Jan 27, 2006

2 1/2 will be fine with your combination. It will also be easier for the bender to make it over the rear axle. I bought my 2 1/2" Flowmaster tailpipes, mandel bent, from Summit--$99 a pair. They are an excellant buy!

As far a H vs X, there appears to be no clear winner--but lots of opinions! H will probably give more low end grunt, and the X gives a more distinct sound at higher RPM's. I decided on the H because it is simple and not in the way when I want to do tranny work. The X needs to be a quality piece to realize the benefits.

Clark · Jan 27, 2006

2 1/2 with Mandrel bent flowmaster pipes and an H pipe if you want a classic deep sound. If not go with an X but you need to hear the difference, it is defintely different.

69 Mach 393 · Jan 27, 2006

Summit has the Magnaflow kit for $475 Stainless pipe and all. How do their muflers sound. Are the Regular 40 Flowmasters to loud to be comfortable in side a street car.

GNN60GT500 · Jan 27, 2006

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

Towards the bottom, they have a sound clip of my Shelby with a 428-

With the Magnaflow kit, the tranny can still be removed without having to remove the exhaust kit-

I am making a little over 300rwhp and 400rwtq- and I saw about a 13rwhp and 14rwtq gain going from the Flowmaster H pipe combo to the Magnaflow kit

Sound wise I think my small block car with the Magnaflow kit sounds very very nice as well-

very little drone when cruising and wide open the thing freakin screams- very crisp sounding-

- I do work for Magnaflow though so I am biased-

302 coupe · Jan 27, 2006

2.5" will be fine, those roush heads don't flow too good on the exhaust side anyway.

bnickel · Jan 27, 2006

if you want to run a full legth exhaust out the back you're pretty much stuck with 2.5", not saying that 3" can't be done but you pretty much have to use a bunch of u-bend pipe pieces and weld them all together to get a good fit with 3" pipes. hell i can't even run the dual "quad" exhaust tips on mine with 2.5" pipe because the tailpipes interfere with the rear shackles so i'm going to have to do some moifications to the tailpipes and the tips to be able to use the tips.

GNN60GT500 · Jan 27, 2006

Actually Magnaflow makes a 3" kit for your car so you dont have to piece one together

ddonaca351 · Jan 28, 2006

2.5 mandrel. (magnaflow kit from summitracing.com - with built in crossover )

Dave-
(if supras can make 6-700whp through one 3" pipe do ya really need 2 of em?)

69 Mach 393 · Jan 28, 2006

The magnaflowe kit is pretty simple but I don't know if I will like the x pipe sound and I'm still conserned they might be a little loud. are the dynomax alot quieter.

dennis112 · Jan 29, 2006

69 Mach 393 said:
The magnaflowe kit is pretty simple but I don't know if I will like the x pipe sound and I'm still conserned they might be a little loud. are the dynomax alot quieter.

I have the dynomax and they are a lot quieter. I run 2 1/2" pipes to the rear with the $99 Flowmaster mandel tailpipes mentioned above. You can listen to the radio and talk to passengers with the windows down UNTIL you nail it. Then the Dynomax's like to do some talking.

69Rcode_Mach1 · Jan 29, 2006

2 1/2 should be fine, if you can get 3" you can do that as well, if you plan on putting a blower or something on it. I went with the Dr. Gas X-pipe and the sound it gives is absolutely amazing. The cam gives it the deep lopey idle, and once you put your foot in it, it screams unlike anything I have ever drive. I definitely prefer X-pipes over H after buying this one especially with the mufflers and headers, it is the exact sound I was looking for. Very Racey, yet grunty, poppy, raspy, just all around mean, think of the Modular engines but deeper and more aggressive sounding.

Clark · Jan 30, 2006

I have the exact same setup as Dennis, I love the dynomax's and everyone says with the H-pipe I have that classic deep sound. When I went to a dyno pull last year, quite a few people came around the corner to see what was making that great sound and enjoy still listening to the radio or talking with my passengers.

86bluecobra · Jan 30, 2006

i would say go 3 inch. you may not need it right now but later you may upgrade or atleast port those heads. I was under the impression that 2.5 inch exhaust was good to 400 poines. i bet you will make more then that with that setup.

bnickel · Jan 31, 2006

86bluecobra said:
i would say go 3 inch. you may not need it right now but later you may upgrade or atleast port those heads. I was under the impression that 2.5 inch exhaust was good to 400 poines. i bet you will make more then that with that setup.

i think that 400hp number is for RWHP, i bet his setup isn't making very close to 400 RWHP. personally i think even my 2.5" system with turbo muffs is pretty damn loud even at idle. the whole neighborhood knows when i start my car as is, i can't imagine running 3" pipes with borlas, flowmasters or magnaflows, in fact i'm seriously considering going with 2-1/4" tail pipes and installing some 30" glasspacks in front of the turbo's just to get it a little quieter and of course so i can use my stock "quad" tips. i should only lose flow at the tailpipes and i may just use some 2 1/2 to 2 1/4 adapters to run the tips.

Max Power · Jan 31, 2006

If you do go 2.5", be sure to go mandrel all the way back. I have 2.5 mandrel with Dynomaxs and an x-pipe and it sounds great but I am getting a little bit of a drone at about 2000-2200 rpm under light load.

GNN60GT500 · Feb 1, 2006

69 Mach 393 said:
The magnaflowe kit is pretty simple but I don't know if I will like the x pipe sound and I'm still conserned they might be a little loud. are the dynomax alot quieter.

Well I have them on both of my cars, and they are quiet when you are cruising and the only time they get really loud is after about 3000RPM- then they are very very loud-

At idle and when cruising though they are not very loud at all-

Help with exaust size

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