Help me plan my exhaust
#2632158
03/13/19 07:37 AM
03/13/19 07:37 AM
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Joined: Jan 2003
Posts: 670 Third rock from the sun.
busboy
OP
mopar
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OP
mopar
Joined: Jan 2003
Posts: 670
Third rock from the sun.
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Exhaust is going on this spring, finally. 70’ Coronet, 440 using Doug’s long tube headers, I’m thinking 2 1/2” off the collectors,then x-pipe and on to the mufflers. Looks like b-body mufflers are center in offset out and reduce to 2 1/4”, I’m planning to use the chrome tips. How big a muffler body can I use, I see them from 14” up to 20” or so. Is bigger necessarily better? We’re planning long (weeks) road trips in the car so not interested in any “drone” at typical highway speeds but would like that nice muscle rumble at idle and slower driving. I realize sound is a very subjective thing but any of your experiences with your exhaust would be much appreciated.
Oh yeah, it's a hybrid.....it burns gas and tires!
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Re: Help me plan my exhaust
[Re: busboy]
#2632267
03/13/19 12:33 PM
03/13/19 12:33 PM
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Joined: Jan 2003
Posts: 20,796 A collage of whims
topside
Too Many Posts
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Too Many Posts
Joined: Jan 2003
Posts: 20,796
A collage of whims
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The longer the muffler case, typically the quieter it is. Same goes for smaller OD tailpipes. Going too long though complicates the tailpipe bend after the muffler as far as clearing the shocks & rear axle. I'm usually 18" max length on mufflers, and for something you don't want to be too loud, look at: Dynomax Super Turbo Magnaflow equivalent Walker "Hemi" muffler I liked the tone of the Dynomax on a fairly healthy 383 RR, not tinny, not too deep, was throaty & crisp. Ran the same on a healthy Hemi RR: headers, H-pipe, full 2.5", modified (2.5 inlet) tips, perfect. The tips seem to sound better than non-tips, my guess is because of their chamber. X-pipe will usually have the effect of smoothing the pulses and giving a higher pitch to the sound. H will leave most of the pulse in there. I'd be tempted to run 2.5" tailpipe on a 440, and tips are available nowadays for 2.25 & 2.5 entry. That said, sound is kind of subjective: on a wagon I did, I tried 3 types of mufflers before I was happy; my exhaust guy still chuckles about that one, but the architecture of a wagon (they're like a drum) complicates that.
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Re: Help me plan my exhaust
[Re: busboy]
#2632279
03/13/19 01:04 PM
03/13/19 01:04 PM
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Joined: Aug 2003
Posts: 43,202 Bend,OR USA
Cab_Burge
I Win
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I Win
Joined: Aug 2003
Posts: 43,202
Bend,OR USA
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Which type and what size motor? If it is a 440 motor and you want the best performance and are willing to mount the mufflers behind the rear end then I would use 3.0 inch kits form Summit and one of several different mufflers brand and type depending on the motors power, no flow stoppers muffs though
Last edited by Cab_Burge; 03/13/19 05:22 PM.
Mr.Cab Racing and winning with Mopars since 1964. (Old F--t, Huh)
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Re: Help me plan my exhaust
[Re: BSB67]
#2633485
03/16/19 10:15 PM
03/16/19 10:15 PM
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Joined: Jan 2003
Posts: 8,398 Highland, MI.
Sunroofcuda
master
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master
Joined: Jan 2003
Posts: 8,398
Highland, MI.
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20" will fit. If you want to lean more to quieter, dyno max 17747 (2 1/4), a little less quiet, 17748 (2 1/2). It is a bit unfortunate the way the exhaust has to pass over/around the exit tube on the "center" outlet muffler pipe. The Ultra flows avoid that, but they get a bit louder.
My observations indicate that you'll have less (maybe no) drone with headers with these mufflers. Your 1970 Coronet had 20" bodied mufflers from the factory. They were offset inlet / center outlets. You could run some 18" resonators at the rear, 4" round body or less will fit. The OE resonators were 4" OD. I would go with Dynomax Super Turbos & 2.5" exhaust.
No Man With A Good Car Needs To Be Justified
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Re: Help me plan my exhaust
[Re: BSB67]
#2634864
03/20/19 03:02 PM
03/20/19 03:02 PM
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Joined: Feb 2007
Posts: 2,578 sweden
1Fast340
master
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master
Joined: Feb 2007
Posts: 2,578
sweden
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20" will fit. If you want to lean more to quieter, dyno max 17747 (2 1/4), a little less quiet, 17748 (2 1/2). It is a bit unfortunate the way the exhaust has to pass over/around the exit tube on the "center" outlet muffler pipe. The Ultra flows avoid that, but they get a bit louder.
My observations indicate that you'll have less (maybe no) drone with headers with these mufflers. The bold part,you bring up a good point however the problem is not as big of a problem on the bigger body mufflers.
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Re: Help me plan my exhaust
[Re: busboy]
#2634876
03/20/19 03:29 PM
03/20/19 03:29 PM
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Joined: Jan 2003
Posts: 17,846 S.E. Michigan
ZIPPY
I Live Here
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I Live Here
Joined: Jan 2003
Posts: 17,846
S.E. Michigan
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For the kind of sound you're looking for I would go with one of the 20" dynomax super turbos.
I think you might enjoy an H pipe a little more than an X style, although I prefer the sound of the X style, I always thought it sounds less old school than the H.
Coming off the collector, Flowmaster sells a reducer cone that drops in size a little more gradually than the norm. It might be a good idea to try those.
Rich H.
Esse Quam Videri
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Re: Help me plan my exhaust
[Re: ZIPPY]
#2634889
03/20/19 04:15 PM
03/20/19 04:15 PM
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Joined: Jun 2006
Posts: 5,163 CT
GTX MATT
master
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master
Joined: Jun 2006
Posts: 5,163
CT
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I replaced a set of 14 inch case Thrush Hush turbos, which neck down to 2.5 or 2.25 inside, with 20 inch case Ultra Flos.
3 inch pipes, dumped at the axles, the longer Ultra Flos are quiter at idle, quieter at cruise, way less drone. Run the longest case you can.
Now I need to pin those needles, got to feel that heat Hear my motor screamin while I'm tearin up the street
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Re: Help me plan my exhaust
[Re: GTX MATT]
#2635711
03/22/19 09:12 PM
03/22/19 09:12 PM
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Joined: Jan 2003
Posts: 670 Third rock from the sun.
busboy
OP
mopar
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OP
mopar
Joined: Jan 2003
Posts: 670
Third rock from the sun.
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Thanks for the replys, very helpful! Been talking with a local shop, gonna run 3” off the collectors, x pipe and into the mufflers. Sounds like a 20” body should give me the sound/tone I’m after. I’ve always like the sound of Dynomax so gonna use those, offset in center out. 2 1/2” tailpipe out of the muffler to a set of stock looking bright tips.
Oh yeah, it's a hybrid.....it burns gas and tires!
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