Horsepower and Exhaust specs

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wazoo64

wazoo64

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Running a 512 ci 670hp and 690TQ
6000 RPM motor with 2 1/2 inch exhaust running through flow masters. Everything I've read says I need 3" exhaust to max top end. Any thoughts?
 
I never gave any thought to go smaller than 3" all the way on my race only 360 that can run 11.20's @ 117 in the 1/4 @ 3,540+ lbs. It includes an X-pipe and Dynomax UltraFlo's. So I'm sure you are being "choked". Hopefully someone has some info on whether or not a 3.5" exhaust should be considered.

Any changes may require a slight jetting change for best results.
 
What size headers are you running as well? 3" will not only let your motor breath better but it will also give it a deeper time as well, it doesn't matter if it's a street car or a track car the motor still needs to breath, two small can hurt the motor with to much back pressure. Just go with a nice h pipe or x depending on the sound you want but 3" to the back, you won't regret it. That's my .02
 
Wazoo, is this on your 64'? Now doubt a 3"-3 1/2" will make more big end power, but what will comfortably fit under a "early A" with the GV & air ride? Let's face it, your making huge power as is, and the big pipes would definitely increase the decibels.....Maybe more then your comfortable with on a "street only" car? I guess what I'm saying is, do you need a extra 20hp versus the increase in sound/noise. Just something to consider...
 
OldmanRick said:
Wazoo, is this on your 64'? Now doubt a 3"-3 1/2" will make more big end power, but what will comfortably fit under a "early A" with the GV & air ride? Let's face it, your making huge power as is, and the big pipes would definitely increase the decibels.....Maybe more then your comfortable with on a "street only" car? I guess what I'm saying is, do you need a extra 20hp versus the increase in sound/noise. Just something to consider...
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This for my 67 coronet. Just got it running and feel like the highway romp is not breathing. The exhaust sounds like its tight. Hard to explain but image that jalopy ghetto pipe sound.
 
Cool! I didn't know it was for a B body. I think a 3" with the right mufflers is just about right for you. I wish I could make a recommendation on the mufflers, but all the good modern stuff is way after my time :). I always leaned toward the quiet side with my exhaust picks, mainly so I could hear the cam/header "ting". I wish you well finding the balance of power & sound. I'm sure some guys here that run current setups can steer you in the right direction.

Enjoy that ride, it sounds like a awesome street car. :thumbrig:
 
OldmanRick said:
Cool! I didn't know it was for a B body. I think a 3" with the right mufflers is just about right for you. I wish I could make a recommendation on the mufflers, but all the good modern stuff is way after my time :). I always leaned toward the quiet side with my exhaust picks, mainly so I could hear the cam/header "ting". I wish you well finding the balance of power & sound. I'm sure some guys here that run current setups can steer you in the right direction. Enjoy that ride, it sounds like a awesome street car. :thumbrig:
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From what I've heard and read magnaflow is best a all around. I'm just really interested to know if I will see a big difference going from 2 1/2 to 3" pipes.
 
wazoo64 said:
From what I've heard and read magnaflow is best a all around. I'm just really interested to know if I will see a big difference going from 2 1/2 to 3" pipes.
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jmo: you definately need 3" . I `ve got 2 -3 1/2" on mine, the benefits are no exhaust leaks, no header gasket leaks, not to mention note choking h.p.
 
i would say 3" with absorbation type mufflers or Hooker aerochambers should be good for your. X or H pipe will tone it down but is up to you what kind of sound you like better.
i would stay away from flowmaster anything.
3½ gets crowded under the car and is very difficult to tone down to a level where it is tolerable.
 
1Fast340 said:
i would say 3" with absorbation type mufflers or Hooker aerochambers should be good for your. X or H pipe will tone it down but is up to you what kind of sound you like better.
i would stay away from flowmaster anything.
3½ gets crowded under the car and is very difficult to tone down to a level where it is tolerable.
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the way I did it, it`s not as loud as flowmasters. this is the second hotrod I`ve done this way. 3 1/2" bullet mufflers, w/ 3 1/2" auger type inserts installed 1/2 in the bullet (roundy-round) mufflers and half out, tach welded inside and 3 1/2" turn downs in front of the rear axle. very low restriction. on my 406 vega, they were 3". I pulled them off for a test after making a few passes, went .003 quicker w/ open headers. thinking most of that was from weight diff. on my 406 gmc, I used the auger inserts only(3"), and it sounded like flowmasters, maybe a hair quieter. haven`t stuck my foot in the 505 yet tho.
 
There is a chart on one of the exhaust threads. I thought I saved it in my favorites. I just remember 371hp was the max for my 2.25 exhaust system.
 
fratzog lover said:
There is a chart on one of the exhaust threads. I thought I saved it in my favorites. I just remember 371hp was the max for my 2.25 exhaust system.
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I know that Dynomax used to have a chart in there catalog and lost somewhere on there website for maximum hp without loss with a bunch of there mufflers. a very good chart just hopeless trying to find it.
 
fratzog lover said:
There is a chart on one of the exhaust threads. I thought I saved it in my favorites. I just remember 371hp was the max for my 2.25 exhaust system.
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Any of these? (But it would be nice if they included pipe size on all of them. But interesting reading nonetheless.))

http://filebox.vt.edu/users/mpyrak/pub/6604983-MufflerComparisionChart.jpg

http://home.comcast.net/~pmahl/mufflers.jpg

http://i43.photobucket.com/albums/e360/Domeskull/mufflerdecibels.jpg

http://www.qsl.net/ya5t/techchart.jpg
 
I ended up going with 3inch Xpipe with 18inch magna flows. I can feel the bump in low end power and the sound is much more bare able than the flowmaster hpipe I had. Money well spent.
 
71scamp78 said:
I don't see how you need any bigger exhaust. The hellcat makes over 800 gross hp and only has 2.75 exhaust
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Not sure how or why but I feel a difference. Maybe the super techs on the site can chime in. I have also been told magnaflow will outperform flow master on the dyno so maybe that's making all the difference.
 
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