It would be great if we had the freedom to run open headers, side-exits, stacks through the hood, or whatever exhaust concoction we pleased to take in the sweet melody of horsepower in all its unmuffled glory. But alas, lawmakers, environmentalists, and the state of California in particular, don’t care much for the idea. Thus, a proper, law-abiding (or close, anyway) exhaust system is critical for any vehicle that is going to spend any amount of time on the road in this and most other states. If you’ve been following along with our Project Biting The Bullitt, you know we’re making great strides toward getting the supercharged, 427 cubic inch 1965 Mustang out to terrorize the freeways and tracks of SoCal. We’ve arrived at the next step in the process where we’ll install a complete exhaust system that will make this 1,000-plus horsepower street car with a race car attitude road-worthy.
And so today, we’re going to take a look at that very exhaust system that will be riding under Biting the Bullitt, which begins with one of Flowmaster’s U-Fit three-inch exhaust systems that we’ll then pair with a set of Flowmaster’s Pro Series mufflers, PerTronix cutouts, and resonators. To help us, Flowmaster’s Nick Tauber and Jim Hairston of PerTronix have chimed in with some great technical details and information on these products and how they best suit our ‘Stang.
Shown here is the entire gamut of components we’re going to be working with on our exhaust install on the ’65, including the Flowmaster U-Fit 3-inch exhaust tubing and Pro Series mufflers, PerTronix electronic cutouts, Y-pipes, Bullet resonators, and a pair of flex joints, along with all of the associated hardware.
DIY With U-Fit
Appropriately named, the U-Fit system is a pre-formed exhaust system that Flowmaster produces that allows gearheads some of the freedoms of a fully custom layout, while taking the cost, time, and effort out of the process of building it from scratch. Simply put, because most people aren’t equipped with the tools or know-how to take on such a project involving mandrel tube bending, the U-Fit provides a do-it-yourself choice without a lot of headache. Beyond that, there are many vehicle makes and models that Flowmaster doesn’t offer a made-to-fit exhaust system for, making the U-Fit a more universal option for those folks.
The U-Fit system features 3-inch (along with 2.25 and 2.5-inch options) 409S stainless steel tubing, pre-bent to a standard layout that can be modified to your particular vehicle. It also comes with the tubes to fabricate the H-pipe, as shown here. Some home brewing is necessary to install the H-pipe, namely cutting the holes and welding the pipe to the main exhaust tubes.
Said Tauber, “The U-Fit Systems are offered as an alternative for people with a vehicle that we don’t produce an exhaust system for. The kits can be made to fit virtually any vehicle.”
The U-Fit Systems are offered as an alternative for people with a vehicle that we don’t produce an exhaust system for. The kits can be made to fit virtually any vehicle. - Nick Tauber, Flowmaster
“There are some unique vehicles out there of which there may not be very many of them on the road and thus wouldn’t necessarily warrant building a kit for them,” continued Tauber. “So the U-Fit is a great way to get the customers a quality piece that they can work with without having to bend the tubing and everything. It’s built to our quality standards, so even though it’s not fabricated for a specific vehicle, it’s still a very quality setup.”
Along with providing a fit for those obscure vehicles for which a kit doesn’t exist, the U-Fit is perfect for those with fully custom builds such as Biting The Bullitt, where the positioning of aftermarket components may not allow for a direct fit of a more vehicle-specific kit.
The U-Fit is a 16-piece complete kit, made of 16-gauge, 409S stainless steel that has been pre-bent and formed to create solid starting point for any DIY project. Flowmaster offers the kits in 2.25-inch, 2.5-inch, and 3-inch dual exhaust sizes to compliment a variety of performance ranges. What you receive with the kit are front adapter pipes, intermediate pipes, the H-pipe assembly (which you’ll have to drill the holes for and weld to each of the pipes), over-the-axle pipes, and a choice of tailpipe exits. Naturally, along with bending the pipes into a suitable universal layout, Flowmaster has also formed all of the pipes with the slip-fit joints for easy connection once you’ve laid the kit out under your vehicle.
What the U-Fit offers, aside from a more universal fit for custom vehicles, is a cost savings for many people. “In some circumstances, the U-Fit would be a more cost-effective alternative than a pre-made kit or having one fully custom made for the vehicle,” explains Tauber.
The U-Fit systems, as Flowmaster’s Nick Tauber pointed out to us, are perfect not only for vehicles that Flowmaster doesn’t make a specific kit for, but for more custom applications like our ’65 Mustang, where you might have aftermarket suspensions like a 4-link, or have specific needs in your layout, as we do with our electric cutouts.
In the case of Biting The Bullitt, Flowmaster produces an exhaust system for the 1964-66 Ford Mustang, but not in a front-to-back three-inch diameter. Because of the kind of exhaust pressure we’re going to be pushing out of the exhaust port, through the headers and out, the three-inch sizing of the U-Fit fits the bill.
“The blown 427 is definitely one of those unique applications that the U-Fit has been designed for,” says Tauber. “You could think of them as specialty vehicles; perhaps you put a four-link in a car or something that no one would offer a kit for specifically, this would be a good alternative.”
Continued Tauber, “We designed these kits to be as universal as possible. The bends that we’ve put in there have been well thought out, as is the way we assembled it. We’ve seen them with a split header on an inline six-cylinder, we’ve seen them routed along the same side of the vehicle, and routed in front of and behind the tires, so there are a lot of ways you can be creative with this kit. There’s no right or wrong way to do it.”
Here, you can see the hole that we’ve cut in the pipes to weld the H-pipe into.
While the U-Fit as it comes out of the box will certainly get you in the ballpark, it does require some custom fabrication and a little tinkering to make it fit your specific vehicle and undercarriage.
As advertised, this kit requires some custom fit depending on the vehicle, and we had to do quite a bit of modification to make it meet our vision for the exhaust system layout on the Mustang, but all in all, the pipes fit together very well. Our primary change involved getting the pipes up and over the crossmember. We also had to purchase some extra U-Fit tubing to complete the dual muffler setup. We cut the U-Fit system to extend back roughly two feet from the tip of the collector, giving us an adequate distance and location for our Y-pipe and cutouts.
The Pertronix Cutouts
These electric exhaust cutouts from PerTronix feature a relatively new design from the company that uses six ball spring plungers to virtually eliminate all leakage, which has always been quite common with cutouts.
Of course, as a street/strip ride, we really want to make this thing free-flow when we need it to to get the most power and torque out of the 427 when we put it in the beams. And naturally, we need to comply with the law on the street, so a set of electric cutouts is a vital part of our exhaust system on the Mustang. After a chat with Hairston and the gang at PerTronix Performance Products, we were on our merry way with a set of their three inch electric exhaust cutouts. These cutouts, which Hairston believes are the very best on the market, are a relatively new design that suit our combo well.
A cutout lives in a very hostile environment and is exposed to a lot of things that can make something fail, but we were able to eliminate the vibration by using six ball spring plungers. - Jim Hairston, PerTronix
“The goal of this cutout design centered on two important things,” said Hairston. “First, we wanted to reduce the size of the cutout — the amount of real estate that it took up under the car. And second, although we’ve had a very low failure rate, we came up with a better seal with the slide-valve design that essentially eliminates any leakage. We’re the only company that does it this way. A cutout lives in a very hostile environment and is exposed to a lot of things that can make something fail, but we were able to eliminate the vibration by using six ball spring plungers that keeps pressure against the gate and doesn’t allow it to rattle.
“Lastly,” continued Hairston, “by reducing the size of the cutouts, we were actually able to lower the cost. We took a lot of material out of it, and because it’s 304 stainless, any little bit of material reduces your material cost substantially. In turn, we were able to reduce our price by roughly 35 percent.”
Hairston has seen these cutouts in use on some pretty stout cars, but suggests always maintaining a distance of at least 18 inches from the tip of the collectors to position it where the exhaust gas pressure is reduced.
Shown here is one of two cutouts with the supplied Y-pipe. These cutouts will serve us well as we transition from the street to the track and back to the street, so that we can deliver a good exhaust flow on the track and make plenty of horsepower, and then utilize the resonators and mufflers on the road where it's needed (and legal).
According to Jim Hairston at PerTronix, you always want to keep the cutouts at least 18 inches downwind from the tip of the header collector to cope with the high exhaust gas pressures. In our case, we've positioned them roughly two feet away from the header. With the Y-pipe installed, we welded a small elbow to each one to allow us to situate the cutouts straight instead of out at an angle.
With our Y-pipe and dual cutouts mounted, we then fit the Vibrant Performance resonator in place, which we opted for to keep down on the exhaust resonance in lieu of a catalytic converter. Because the car is considered an early model vehicle per California DOT, we’re able to run without the cats, but mufflers are a must.
Pro Series Muffler
The Pro Series muffler is a round case design that departs from the familiar “Flowmaster sound,” with a deeper, less hollow tone.
Sticking with the Flowmaster theme, we’ve finished Biting The Bullitt’s exhaust system out with their high-flowing Pro Series mufflers, also measuring three inches in diameter, These new mufflers are highly versatile, with technology and performance suited to the street or the race track. The Pro Series mufflers are round case designs, with a “shorty” 12-inch as well as a more standard 16-inch and 20-inch version available (we’re using a standard 16-inch by three-inch version on our Mustang), with a straight or turndown outlet. Like the U-Fit, these mufflers are made from the same high quality 409S stainless steel.
Flowmaster's Laminar Flow Technology
The Laminar Flow Technology that Flowmaster has built into the Pro Series muffler departs from the traditional straight-through muffler design by using two perforated cones that allow for control of how the exhaust gases flow through the muffler. Because of the way that exhaust gases are pushed out of the combustion chambers, the flow is turbulent and pulses through the pipes. Because traditional mufflers don’t control the pulses, the sound can be difficult to control. But by utilizing these cones and changing their angles and the perforated patterns, the muffler can be adjusted to specific sound and performance characteristics. In doing so, a low pressure zone can be created that improves the exhaust gas scavenging and controls the flow of the turbulent exhaust gases.
“The Pro Series sports a new type of technology that we’ve introduced, known as Laminar Flow, in which the muffler placement within the exhaust system isn’t as critical to helping with the scavenging of the exhaust gases,” explains Tauber. “So, it’s more versatile in that effect. Because these mufflers don’t rely as much on pulses, they’re very well suited for turbo applications.”
The Pro Series also boasts what Flowmaster calls “Coll Shell” technology that provides a low exterior operating temperature. As Tauber explains, “it minimizes the radiant heat produced by the muffler. In turn you can place it closer to the floorboards without experienced excessive heat issues.”
All specifications and marketing jargon aside, what most gearheads really want to know when it comes to mufflers is, what do they sound like? For the answer, we turned to Tauber, who in fact has a set of these on a couple of his own personal vehicles.
“These do have a different type of sound than the classic Flowmaster chambered muffler. It’s a deeper, more bass-like tone — more of a solid tone. Flowmaster’s are known for their more hollow tone, but these are deep.”
On Biting The Bullitt, the Pro Series mufflers are mounted to the outlet of the resonators and set up to face diagonally away from one another at about a 10-degree angle.
These images provide a glimpse at the final stages of the installation and the final product. You can see here the flex joints that we installed in the pipes, and the final step of welding the pair of Pro Series mufflers to the U-Fit pipe.
What our new exhaust setup on the ’65 gives us is truly the best of both worlds in that we can fly under the California DOT’s radar and not draw too much attention to ourselves in terms of noise, while still flowing quite well for the kind of power we’re producing. When it comes to the track, we can slide open the electric cutouts and really let this thing flow wide open, without concern for noise, to get the best performance, and therefore elapsed times, possible.
With the full exhaust installed, our supercharged ’65 Mustang sounds like a tame musclecar, that is, until we open up the cutouts!