MAC Dual Exhaust w/ Pacesetter H-Pipe Adapter
rdBy: Chip Bulkeley. Original Article Posted March 3, 2006 thUpdated: January 17, 2007
Cat back dual exhaust, what every V6 Mustang gear head dreams of. Why? As Tim “The Tool Man” Taylor would say, Power, more power. Arrgh, Arrgh,
I decided to install my cat back dual exhaust system for the same reason, more power. One of the main considerations when deciding on how you want to achieve your final goal is; should I do it myself or have an exhaust shop fabricate it for me? I like to do my own work when it is feasible, and there are several manufacturers out there that have cat back dual exhaust systems that you and a buddy can install in your driveway or garage. I selected a manufacturer that I had some previous experience with (the MAC 3.8L V6 CAI system) and offered a product that could easily be installed by my self. I chose the MAC Flowpath 2.5” cat back dual exhaust system, part #TK7995 with True Fit? joints, more on this feature latter. I will not discuss every step of the installation, only those things I think need greater explanation or are not obvious from the instructions. I use the terms right side/passenger side & left side/drivers side as well as speed nuts/blind nuts interchangeably, honestly I am not trying to confuse anyone, but sometimes certain words just seem to make more sense than others.
The first order of business for the installation of any cat back dual exhaust system on 1994-2004 V6 Mustang is the selection of a dual exhaust adapter. There are very few choices available at the present time. By far the most popular and well known adapter is the Pacesetter Exhaust Products H-pipe adapter kit available from a variety of sources, I purchased mine from Steeda. As you will see in the photos, the fit and finish of the H-pipe adapter is very good. The instructions are adequate. By that I mean that with the technology that exists today, they could be upgraded and clarified, but I had no problems with the installation. One other note regarding the Pacesetter kit; the instructions assume you are installing a Pacesetter TFX? Performance Kat-Back System, that’s what ththose extra little brackets and rubber isolators are for. As of January 17, 2007,
there is a new H-pipe adapter available from MAC. It is the Catted H-pipe adapter kit that removes the pipes that run from the headers to the exhaust and replace it with new high flow Cats and an H-pipe assembly. I have included a photo of this product at the end of the photo section.
When the MAC dual exhaust kit arrived, I assembled the H-pipe adapter and dual exhaust system on my shop floor just to get a good idea of how it all should fit together before I started tearing my Mustang apart. You just don’t want any
surprises during assembly. One thing I did discover is that the flange bolts
provided by Pacesetter for the H-pipe to cat back connection where too long. So I dropped by my local Big Box home store a purchased four 3/8” Grade-8 bolts
that were 1” shorter that the ones in the kit. Perfect!
There are a few other items that will need to be purchased before you can complete the assembly such as; high strength thread locker (I used Permatex? RED PX #27100) and some high temp grease (I used Mystik JT-6 Part No. 5438-79 NGLI No.2*) to lube the MAC True Fit? joints to enhance ease of installation. Also purchase a small tube of Permatex? Anti Seize Lubricant to coat the crossover tubes that make up the “H” in the H-pipe adapter.
I have included a list of the Ford part numbers for all of the exhaust hangers found on a GT model Mustang:
Exhaust hangers are available from you local Ford dealer.
Right side muffler hanger part number is: E6ZZ-5C263-A, $16.73
Right side tailpipe hanger part number is: F4ZZ-5A246-B, $21.57
Left side muffler hanger part number is: E6ZZ-5260-A, $16.76
Left side tailpipe hanger part number is: F4ZZ-5256-A, $22.57
You may be able to get these parts at Year One, Mustangs Unlimited, Late Model Restoration or else where for less (remember you will have to pay for shipping). I chose to install all new hardware rather than mix 121,000 mile rubber hangers (left side) with new ones (right side). After I removed the old hardware, I noticed very little difference between the old rubber insulators and the new ones. Did I install the new ones? Absolutely! These were special order and I was stuck with them, but hey they look real nice under the car. The Ford dealership I ordered from did not have the bolts or anchor nuts I needed so I ventured out to my local auto parts store and purchased a set of M8-1,25 x 25mm tapered bolts (4) and one pack of U-Type M8 speed nuts (blind nuts). The particular brand I purchased had two M6 and two M8 speed nuts per pack, you will only need the M8s, more on this point in the photos below.
Okay, time to get started. This could have been easily completed in my shop with the jack stands at full vertical extension (about 18-20”). I have made several
small tweaks of the exhaust system in my shop, on my back with absolutely no problems at all. There is plenty of flexibility built into the MAC product to allow for maximum “tweaking”. I will tell you right up front that I completed the installation on a vehicle lift only so I could shoot the photos for this article. By the way, I dropped my digital camera early in the project so some of the photos in this article were taken about a week later.
Start by measuring and cutting the Y-pipe as per the Pacesetter instructions, the measurements are precise so there is no need to “fudge” them one way or another. I cut the Y-pipe using my cutoff tool and a hacksaw. If I had it to do over again, I would use a Sawzall? type tool with the proper blade. Disconnect the rest of the old factory exhaust back to the tailpipe and discard. I’m no tree hugger but, if at all possible, find a recycling or scrap metal company that will take the old exhaust parts. Try not to dump them in a land fill. OK nuff said on that.
Take some of the anti seize lubricant that you have and liberally apply it to each end of the exhaust pipes that remain after the Y-pipe was cut away, as well as the inside of the crossover tube on the passenger/right side of the H-pipe adapter. This will help every thing side/rotate more easily when pulling together the H-pipe parts under your Mustang. I started my assembly by sliding the left side H-pipe tube onto the OEM exhaust tube almost up to the base of the O2 sensor threaded bung. That’s right, it’s called a bung. Next, I slid the right side H-
pipe tube onto “bent” OEM exhaust tube at a 45 degree angle down ward toward
the centerline of the vehicle. Now, what you need to do is rotate the two halves of the H-pipe assembly together at the crossover tube. The two tubes may not match up precisely; mine did not, so I used a 2lb hammer and a piece of hardwood to persuade the two pieces together. I did not end of with a perfect “H” when I was done; actually it was sort of “A”ish with the crossover measuring 5”.
When it was time to connect the cat back exhaust, I had no problems getting every thing to fit.
The H-pipe kit comes complete with saddle bolts (“U” bolts) for clamping the H-
pipe to what is left of the Y-pipe. I installed them initially and then latter removed them when I realized that they did not seem to perform a useful function. Let’s be honest, you cannot apply enough torque on the saddle bolts to deform the H-pipe onto the old y-pipe. My installation leaked on the left side and a little bit at the crossover tube, so I had a local exhaust shop weld all three joints together, and no more leaks.
Now onto the rest of the install, the next thing to do is to install the new exhaust hangers. For the purposes of this article I will discuss all four hangers starting with the passenger side muffler, since we are starting from scratch on the passenger side of the car, I will be going into this with more detail than on the driver side. Remove the driver side muffler hanger, set it aside, and then remove the inboard (nearest to the drive shaft) blind nut. That’s right; I said the driver’s
side. You are going to need the blind nut to use on the passenger side muffler hanger. Take the blind nut and install it at the outboard position on the passenger side (see photo below). Now remove two of the M8 blind nuts you purchased at the auto parts store and place them at the inboard positions for both of the muffler hangers. Install both of the muffler hangers, done.
Next thing you will need to do is install the rear tailpipe hangers. Start by taking one of the M8-1,25 x 25mm tapered bolts and thread it into the passenger side tailpipe hanger predrilled hole and run it all the way to the bolt head. The 1994-2004 Mustang bodies were all built to be either Cobra; Mach 1, GT or Coupe assemblies. Pretty cool huh? Install the tailpipe hanger and tighten, no need to repeat on the drivers side and you are finished.
At this point you will want to install the “L” shaped tailpipe drops into each of the respective tailpipe insulators. Don’t use too much grease when install these
pieces, later on they will slide around too much.
Take the flow tubes and loosely connect them to the H-pipe adapter after applying a liberal coat of high temp grease, no thread lock yet. Don’t worry about
the grease burning when you light off the engine, it will wash off long before it burns. The True Fit? joints provide for a large amount of adjustment while installing the system. Hang the driver and passenger side Flow Path mufflers in their respective hangers, then loosely connect the flow tubes to the mufflers. Again, no thread lock yet. Time for the chrome tailpipe extensions, both sides, loosely fit. Slide the stainless steel band clamps onto the inlet end of the 3’ tailpipes, slide tailpipes onto the extensions, tighten band clamps (loosely), connect the tailpipes to the “L” shaped drops (slide nut head into welded channel) and take a break.
Okay, okay, back to work! Now is the time to start gradually tightening up the nuts and bolts from front to rear, no thread lock yet. As you work your way back, pay special attention to the upper and side to side clearances on the pipes and mufflers. There is no certain way this should be done other than the assembly should not make any metal-to-metal contact when shaken side-to-side, up and down. What you are basically doing is simulating the vibration the exhaust system will experience as you drive down the road. When you are satisfied that every thing is in the proper positions tighten all the bolts down and see how it looks. If you are happy with the install, one-by-one loosen one nut/bolt at a time and apply the thread lock. Repeat until all of the nuts and bolts are treated with a good coat of the thread locker.
So how does it sound? Well it does not sound like an import tuner with a fart can. It does not sound like a V8. It sounds like a V6 with an awesome cat back dual exhaust installed. It sounds good! So why doesn’t it sound like a V8? Well
there are several reasons for that. To begin with, the exhaust pulse on a V8 occurs once during each 45 degrees of crank rotation, on a V6 this occurs every 60 degrees of crank rotation. Secondly; the V8 displaces 0.575L of gas during every exhaust pulse, where as the V6 displaces 0.633L. Finally, even though the V8 displaces a lesser amount of gas per exhaust pulse, it does displace a larger overall volume of gas per crankshaft revolution than the V6.
That is why the V8 is a bit more “throaty” than the V6 as well as the fact that there is a shorter duration between exhaust pulses on the V8. This should help further explain why a Harley sounds the way it does. Additionally the V6 is and even firing engine and the V8 is an un-even firing engine. This is not an all
encompassing explanation of why engines the way they do, but it should provide a basic explanation of some of the factors.
So how does it run? The first few drive cycles were a bit sluggish. This was primarily due to the fact that the computer needed to schedule more fuel as a result of the increased air flow. Without having put it on the dyno, I would say the torque curve has changed dramatically, peaking at a higher rpm than the single tube exhaust (this would be later confirmed on the dyno run in November 2006). I would also have to say that the horsepower curve has changed as well. I will be posting the dual exhaust dyno run results on the performance page in the future.
This was a really fun project. I had several bubbas peeking under the car to see how I was going to hook up a dual exhaust to a V6. They thought it was pretty cool too.
As an addendum to this article, I offer the following comments. I received several e-mail responses with regard to the V6 dual exhaust project, all were positive, with a few asking the question: “is this the only cat back system that will
work on the 3.8L V6 Mustang?” No, absolutely not. Any Mustang GT cat back dual exhaust system should work on the V6 just fine. If the manufacturer’s text does not explicitly state that it will work on a V6, ask. Write, phone or e-mail the folks selling the product you are interested in and remember that price is also a factor in deciding what system to purchase.
I hope you decide to take on this project; it is well worth the effort. Good luck!
Copyright ?2006 CHiP’S V6 Specialties LLC
The Pacesetter H-pipe dual exhaust adapter, the small box contains the
rest of the attaching hardware.
There it is, mocked up on my garage floor. This is how I discovered that the flange bolts provided by Pacesetter were too long for this particular cat back system. The adapter flange bolts may work just fine on another model
or brand of cat back system.
A few of the additional items that I purchased for this project.
This is how your Y-pipe should look after you make the cut off marks as
detailed in the Pacesetter instructions. You can use chalk or an “oil stick”
to mark the exhaust pipes.
This is the view after cutting the Y-pipe and fitting in the H-pipe. You can
see the brake line heat shield supplied in the Pacesetter kit (it’s just above
the right side flow tube in this photo.