Planning out a new exhaust system

[Pontiac787]

Hi all,

I’m starting to plan out a new exhaust system for my 1967 Mustang and I wanted to get some feedback.  The engine is a fairly stock 427.  The car is a driver/cruiser.  The current system is a straight shot of 2.5” pipe from the headers to 16” turbo mufflers then a 2.25” stock
Below is my current plan and rational.
tailpipe with twin tip resonators.  There is no crossover pipe. 

2.5” mandrel bent pipe – should provide sufficient flow while providing more room for the install
H pipe – From what I’ve read, an H pipe will produce better torque for a street/cruising application opposed to an X pipe.
Dynomax Super Turbo with a 16”or 20” case (17629, 17749) – provides good flow without being annoyingly loud

I like the twin tip look so I may add 2.5” flowmaster tips https://www.flowmastermufflers.com/accessories-and-tips/15307-exhaust-tip-300-in-dual-angle-cut-polished-ss-fits-250-in-tubing-clamp-on/  or 2.5” Jones resonator tips.  https://www.jegs.com/i/Jones-Exhaust/523/JDR212/10002/-1  Jones is the only brand I could find with a 2.5” inlet. 

Originally, I was planning on going with the Magnaflow 15816 Kit https://www.magnaflow.com/products?partNumber=15816 with an X pipe .  I really like the stainless but from what I have been reading this setup will provide good peak power but it kicks in later in the RPM band so might not be as much fun for cruising.  I was also concerned that the Magnaflow Street Series mufflers would be too loud for my taste. 

I have no firsthand experience with any of these products so any insight would be appreciated.  Also, does anyone know if someone sells an application specific stainless exhaust kit minus the mufflers?

[cattleFEeder]

https://www.summitracing.com/parts/pye-sfm03/overview/year/1967/make/ford/model/mustang
I have this brand on my 73 mustang with a 393C stroker. Fits well,  nice quality and don't worry about the Xpipe on a street car they work great.

[My427stang]

The H versus X pipe is generally academic and in the end I have seen very little difference.  My advice, use what you think will fit nicely.

On my Mustang I used a 3 inch exhaust with a 3 inch H crossover because it fit well, I tried to put an X in there a few times over the years and I never liked how low it hung. 

On my F100, I built a 3 inch exhaust, and used a 3 inch X pipe, becuase I could fit one and wanted to try it.  I certainly gained low rpm part throttle, just like an H

In the end, both will do great and help part throttle, low to mid RPM performance. X pipe has a little different sound, but my exhausts are so different (Borla Pro-XS with an H behind a 489) and (Jones with an X-pipe behind both a 445 and a mild 390) that it is very hard to compare.

I say either, but be sure to use one for a street car

[machoneman]

I'd offer that of all the testing I've seen any differences (on a muffled car) are minimal at either rpm range. That said, X's apparently do provide a tad more hp at high rpms in unmuffled vehicles. Both though are superior to a system that uses neither.

And yes, the X-s in many muscle cars sit quite low if installed after the headers, preventing many, like me, from using it.  H's are also a tad easier to remove when yanking the tranny or clutch for maintenance.
 
H pipe – From what I’ve read, an H pipe will produce better torque for a street/cruising application opposed to an X pipe.

[Rory428]

I am also contempating what to put for an exhaust system under my 59 in the (hopefully) near. I have a basically stock 428 Cobra Jet engine with a mild solid flat tappet cam (228@.050", .530" lift), Performer RPM intake,780 vac Holley, and FPA headers. It will be mainly a street car, with a few trips to the dragstrip every year, so I do NOT want a obnoxious or loud exhaust system, and with 3.50 gears and a wide ratio Toploader, (no OD), it will be probably 2600 RPM at highway speeds. I am leaning towards a full 2 1/2" system to the rear bumper, and am also considering mufflers like the Dyno Max turbo style, as I do not like the sound of glass packs or Flowmasters. I have also heard that the Hooker Aerochamber mufflers are pretty good, but I am not aware that I have ever heard them. I suppose mufflers and crossover pipes are subjective to personal opinion, but I have never much cared for the sound of an Xpipe, sounds a bit too "shrieky" to me, and often makes it sound like the engine is revving higher than it actually is. On both my low compression 390 with long tube headers and Raptor turbo mufflers, in my 74 F350 car hauler, and on my old street strip Fairmont with a warmed up 302 and 5 speed, using Hedman long tube headers, no cats, with factory 5.0 Fox Mustang mufflers and tailpipes, I first ran them with no H pipes, and later added a 2 1/2" H pipe to each vehicle, and frankly I can not say that adding the H pipes made any noticable differance, go or bad. And on the Fairmont, with ran low 13s and high 12s, there was no changes on the ET slips. I do know that the factory H pipes on my 69& 70 428CJ Mustangs did have a crossover, but the crossover was curved & considerably smaller than the main exhaust pipes (maybe 1 1/4-1 1/2" crossover pipe diameter), so maybe the straight 2 1/2" crossover on my truck and street Fairmont was too large? Also at my 428s power level (382 HP), I do not think going to a larger, louder, and much more expensive and harder to install 3" system would be worth the effort, any thoughts? As for the prefabbed Mustang Pypes  tailpipes, are they suposed to fit with both the regular rear shock arrangement, as well as the staggered shocks? That could also be something to consider.

[Pontiac787]

Thanks for the replies.  I think that most of the kits I’ve seen specify that modifications would be needed to use with staggered shocks.

[cammerfe]

I have a Magnaflow cat-back on my Lincoln LS land speed record-holder/daily driver. It is NOT too loud. Just sorta 'mellow'. Take that as you will.

Some years ago I put a custom bent 321 SS 3" system on my '63 Effie/390-330 PI combo. I had long iron exhaust manifolds and factory flanges I adapted to the 3" pipe. I had the guy running the Huth run the two pipes together and made an oval cut on each pipe and then joined the ovals as a sort of X. I used 3" Bassani mufflers. I had a number of comments about the excellence of the sound.

(If I had it to do over again, I'd remove the driveshaft and install the pipes bent up so that the DS would go below the 'X'.)

I'm a strong believer in using an 'X'.

KS

[TomP]

I was at the KMS Tools car show today and checked out the exhaust bits in their auto section. They have mandrel bent "S" shaped pipes, 3 or 4 feet long that would make exhaust fabrication easy. Looked like 2 1/2" and 3" were both there,. Plus the normal U bends and straight pipes. Those offset pipes coming off the headers would save a lot of ugly cuts and welds.

My biggest gripe with all this stuff is it's 16 ga. Like bridge girders, heavy but also it won't flex so it pulls on the hangers and headers when the engine moves. I think original exhaust was 18 or 20 and there is no reason for stainless to need be thicker than 20 ga.

[Pontiac787]

Now I'm thinking that the 17749 is going to be too quiet so I'm looking at the Dynomax Ultra Flo 17513.  This is a straight through design with a 20" body.  I'm thinking the 20" body will flow better since the angle of the pipe in side will be less abrupt but it will be a little quieter at the same time.  Does anyone have experience with the Ultra Flo's?

[My427stang]

Not only will it be quiet, it will be down on power.  The best muffler out there is the Ultraflow design (also Magnaflow, Jones, Borla ProXS, Hooker Maxflo)  plenty quiet when you want to behave, nice sound and will make more power.

I wouldn't worry much about the angle of the tube, but the design itself is proven

[cjshaker]

I'd like to see just ONE documented experience where an X or H pipe lowered an ET number. Yes, dynos show a fairly small advantage, but hardly "superior" as Bob mentioned. Still, I have not seen one ET slip to prove it makes an actual difference on the track, which is where the truth is going to come out. And like Rory, I've tried them and could not feel any difference at all. But to listen to almost everybody on the internet, we should be amazed that engines even run at all, without them

[Heo]

. But to listen to almost everybody on the internet, we should be amazed that engines even run at all, without them
[/quote]

Like the expert when i was at a carshow that told anyone around him that my
rod was not driven there because it would not even start with my exhaust manifolds
due to  different length tubes. (Lakestyle headers 4 tubes dumping in to a megaphone )
I talked to him and asked, Oh  you know a lot about engines? Yes the tubes have to be
equal length otherwise the engine wont run . It would not even start someone just towed it
here just to show of
I know that because i built racing engines my whole life you see,
He said with a high voice so everybody should hear him.....
I said i understand your an real expert on this,  jumped in flicked the ign switch
pressed the starter button smiled at the laughing audience and drove of with smoking tires

[machoneman]

OK! Guilty as charged! 
Seriously, perhaps better than no H or X is what I should have said. I mean, various Ford and GM cars did get an H right from the factory and I'd venture the extra 50 cents in metal meant that they did get something for the effort. Could be though a reduction in sound rather than a performance increase.

I'd like to see just ONE documented experience where an X or H pipe lowered an ET number. Yes, dynos show a fairly small advantage, but hardly "superior" as Bob mentioned. Still, I have not seen one ET slip to prove it makes an actual difference on the track, which is where the truth is going to come out. And like Rory, I've tried them and could not feel any difference at all. But to listen to almost everybody on the internet, we should be amazed that engines even run at all, without them

[HvyFt4spd]

 I think that's your connection, the hamonic cancelling allows for a more free flowing design that would otherwise be pushing the decible level. Think about it in terms of making the entire exhaust system one big flowmaster muffer. Equalizing pressure or some pulse overlap may be happening there as often pressed, IDK. I have had times were adding an H or X to an existing exhaust system felt like it did something. What I've also noticed is that at times I was driving by ear and running the engine harder now that the system was quieter so it obviously was making more power being run at a higher rpm.. No series of slips either, generally just people that read magazines and decided they needed one.

[JamesonRacing]

Now I'm thinking that the 17749 is going to be too quiet so I'm looking at the Dynomax Ultra Flo 17513.  This is a straight through design with a 20" body.  I'm thinking the 20" body will flow better since the angle of the pipe in side will be less abrupt but it will be a little quieter at the same time.  Does anyone have experience with the Ultra Flo's?

I have Dynomax Ultraflows on my 66 Fairlane street car, 465 inch FE, 3-1/2 off the headers to the X, 3" to the mufflers, 2-1/2" Flowmaster tailpipes.

The drone at 2K RPM was more than annoying.  The car was quieter at 6.5k than when I was cruising in fifth gear.

I bought two Spintech 3" short race mufflers and cut them in midway between the X and the Ultraflows.  Made all the difference in the world. 

I wouldn't use Ultraflows again personally.  I'd spend the money and go with the Borla offerings, using as long a muffler as you can fit under the car.