Flowmaster pioneered the art of exhaust acoustics. We've all experienced that Flowmaster phenomenon at one time or another, hearing the throaty "warble" of virtually any V-8 through dual mufflers and instantly recognizing them as Flowmasters. The "Flowmaster sound" is the epitome of American muscle car power.
Flowmaster's legacy goes back to 1983, when Sprint Car racers in California were faced with tough noise legislation. Flowmaster founder Ray Flugger developed a muffler that would quiet racing engines without compromising performance. At first, Ray's exhaust silencers were downright ugly. He even welded handles to them to make them easier to carry during testing. They became known as "suitcase mufflers," but their design was ultimately patented, the result of years of testing in very modest beginnings.
Those first Flowmaster mufflers came from a small barn in Northern California. Today, the company produces mufflers and exhaust systems from its state-of-the-art manufacturing facilities. In fact, Flowmaster operates the only research and design facility of its kind, using a SuperFlow SF-7100 engine dynamometer for testing. Ray Flugger remains active in the company, keeping a close eye on the legacy he created nearly three decades ago.
Flowmaster offers several choices for the Mustang's 45 years of production. That means there's a Flowmaster muffler designed specifically for your Mustang. Which type should you choose and why?
First, you need to choose either an entire exhaust system or a pair of Flowmaster mufflers that will fit your Mustang's existing pipes. Flowmaster does entire exhaust systems for all Mustangs except the '74-'78 Mustang II. This means complete systems for '65-'73 classics, '79-'04 Fox-bodies, and '05-'09 cars.
There are two basic Flowmaster American Muscle exhaust systems available with 2 ¼- or 2 ½-inch pipes for classic Mustangs. Two important points: They will not fit convertibles, nor are they compatible for the '65-'66 GT valance panel with trumpet tips. They employ late-model-style exhaust hangers. If originality doesn't matter, they offer an improvement over original equipment because they isolate noise and vibration better. If you must have original pipes and hangers, go with one of Virginia Classic Mustang's factory original-style exhaust systems and fit it with a pair of Flowmaster mufflers. We're going to show you both ways.
This is the Flowmaster two-chamber...
This is the Flowmaster two-chamber Series 40 muffler for classic Mustangs. If you like a throaty roar, the original two-chamber Flowmaster muffler, available from Virginia Classic Mustang, is for you. Be advised, these guys are loud with a lot of interior resonance. But you just can't beat the demeanor of the Flowmaster. Available in 19- and 23-inch lengths with two different types of pipe offset, they're a good fit for '65-'04 Mustangs, including '74-'78 Mustang IIs. All you need is a good exhaust shop that can do custom pipe bending.
Here's the Flowmaster Series...
Here's the Flowmaster Series 50 muffler (23 inches long as shown) which will fit underneath your classic Mustang, but it gets tight. Count on trimming tail and exhaust pipes for a good fit. The three-chamber Series 50 is quieter with a deeper sound.
Here's the 19-inch versus...
Here's the 19-inch versus the 23-inch overall length difference. The 19-inch Flowmaster is a perfect fit for '65-'70 Mustangs. The 23-inch muffler is a tight fit but works great with '71-'73 Mustangs.
This is our Turbo dual exhaust...
This is our Turbo dual exhaust system from Virginia Classic Mustang. We have removed the old mufflers to install 19-inch Flowmaster Series 50 Delta Flows. For the Delta Flow muffler to fit properly, we had to cut 2 ½-inches off the exhaust pipes to get our tailpipes and mufflers properly positioned.
Because 2 ½-inches...
Because 2 ½-inches gets into the exhaust pipe bend, Sergio's Muffler in Palmdale, California, had to both cut and expand the pipe end to properly fit our Flowmasters.
Our old mufflers had welded-on...
Our old mufflers had welded-on hanger brackets. Flowmasters do not, which presented us with a challenge-how to hang the exhaust system. AutoZone has two types of muffler hangers available from Hang-It-All. We suggest using the PN 17146 hanger kit (you will need two of them). All you will need is the pipe bracket (shown at the top here on the Virginia Classic Mustang factory muffler hanger). Modify the pipe bracket as shown and attach it to the factory hanger. At the bottom is the Hang-It-All PN 17175 hanger, also available from AutoZone stores. You can use the pipe hanger from this kit as well.
Here's the factory hanger...
Here's the factory hanger with parts from the Hang-It-All kit (PN 17146). Spacers are available at Lowe's or Home Depot to achieve proper height. If your Mustang originally had factory dual exhausts, you won't need spacers, just the modified pipe hanger bolted to the insulator.
This is the basic Flowmaster...
This is the basic Flowmaster American Muscle series exhaust system for '65-'70 Mustangs. For '65-'66, you get a stainless steel tailpipe tip and a choice of either 2 ¼- or 2 ½-inch pipes. For '67-'70, you get a 2 ½-inch pipe system with either GT valance (great-looking stainless tips) or non-GT valance (with turndowns).
Here's the hardware that Flowmaster...
Here's the hardware that Flowmaster provides with the American Muscle exhaust system. The hangers are late-model style, which isolates noise and harmonics better. However, they are not like original equipment. You can use this hardware kit or the factory original-style exhaust hanger kit from Virginia Classic Mustang.
|Quick Mustang Reference Guide|
|To Flowmaster Mufflers|
|Muffler Type||Part No.||Specifics|
|Series 40 Two-Chamber||42443||2 ¼" in/out Offset Both Ends 19" Overall Length|
|Series 40 Two-Chamber||42441||2 ¼" in/out Offset In/Center Out 19" Overall Length|
|Series 40 Two-Chamber||42543||2 ½" in/out Offset Both Ends 19" Overall Length|
|Series 40 Two-Chamber||42541||2 ½" in/out Offset In/Center Out|
|Series 40 Delta Flow||942041||2" in/out Offset In/Center Out 23" Overall Length|
|Series 40 Delta Flow||942441||2 ¼" in/out Offset In/Center Out 23" Overall Length|
|Series 40 Delta Flow||942443||2 ¼" in/out Offset Both Ends|
|Series 40 Delta Flow||942543||2 ½" in/out Offset Both Ends 23" Overall Length|
|Series 40 Delta Flow||942541||2 ½" in/out Offset In/Center Out 23" Overall Length|
|Series 40 Delta Flow 409||842441||2 ¼" in/out Offset In/Center Out 23" Overall Length|
|Series 40 Delta Flow 409||842443||2 ¼" in/out Offset Both Ends 23" Overall Length|
|Series 40 Delta Flow 409||842541||2 ½" in/out Offset In/Center Out 23" Overall Length|
|Super 44 Two-Chamber||942448||2 ¼" in/out Offset Both Ends 19" Overall Length|
|Super 44 Two-Chamber||942548||2 ½" in/out Offset Both Ends 19" Overall Length|
|Series 50 Delta Flow||942051||2" in/out Offset In/Center Out 23" Overall Length|
|Series 50 Delta Flow||942451||2 ¼" in/out Offset In/Center Out 23" Overall Length|
|Series 50 Delta Flow||942456||2 ¼" in/out Offset In/Center Out 19" Overall Length|
|Series 50 Delta Flow||942453||2 ¼" in/out Offset Both Ends 23" Overall Length|
|Series 50 Delta Flow||932556||2 ½" in/out Offset In/Center Out 19" Overall Length|
|Series 50 Delta Flow||932551||2 ½" in/out Offset In/Center Out 23" Overall Length|
|Series 50 Delta Flow||932553||2 ½" in/out Offset Both Ends 23" Overall Length|
|NOTE: These mufflers apply strictly to Mustang. Three-inch pipe mufflers are not included because they are not recommended due to space concerns.|
Complete Flowmaster Exhaust Systems
Complete Flowmaster exhaust systems are available from Virginia Classic Mustang for classic and late-model Mustangs. If you're doing a classic, there are four basic systems designed to fit: two for '65-'66 and two for '67-'70. All are from the transmission crossmember back. If you have a convertible, you're out of luck because these systems are designed for hardtops and fastbacks only. Late-model systems (not covered here) are from the catalytic converters back (known as "cat-back" or "after-cat") with the H-pipe, mufflers, tailpipes, and all attachment hardware.
The 19-inch Flowmaster Series...
The 19-inch Flowmaster Series 50 Delta Flow mufflers are a perfect fit.
The American Muscle system...
The American Muscle system (PN 17334) comes with the shorter Series 50 Delta Flow muffler, perfect for a frequent-driver classic Mustang. These are 19 inches long with 2 ¼-inch offset in and center out. This is where it gets tricky because '65-'66 Mustang factory dual exhausts are center in and offset out. With the Flowmaster system, there are no worries about offset. If you are fitting them to a factory '65-'66 exhaust system, you may need a muffler shop to tweak your pipes for better fit.
Externally, the Delta Flow...
Externally, the Delta Flow muffler doesn't look any different from a conventional Flowmaster. The difference is inside. Here's a pair of 2 ¼-inch Delta Flow mufflers that are 19 inches long. We had these custom-made by Flowmaster for '65-'66 factory dual exhausts with center in and offset out. You'll have to pay more for this feature, but it's worth it if you want to keep the original pipes.
Delta Flow magic is inside...
Delta Flow magic is inside with multiple deflectors, a resonant tuning chamber, power chamber, and a low-pressure balance chamber. The result is a more civilized Flowmaster muffler with a quieter cabin and less resonance.
The H-pipe, with its crossover...
The H-pipe, with its crossover tube, should always be used with a dual exhaust system to balance cylinder bank exhaust pulses and improve sound.
Pro Motorsports Engineering...
Pro Motorsports Engineering pioneered the X-style crossover. The X smoothes out exhaust pulses and yields better scavenging, especially at high rpm. It also quiets exhaust harmonics and improves horsepower. Don't expect a huge gain in power, however. On average, we've seen 5-15hp improvements. Expect closer to 5 hp. Mix the X crossover as part of your horsepower improve arsenal. It's the little things that add up to big gains. On the street, torque is what you want most.
|17273||2 ½" with Series 40 Delta Flow Mufflers and polished stainless tailpipe tips.|
|17334||2 ¼" with Series 50 Delta Flow Mufflers and polished stainless tailpipe tips.|
|17281||2 ½" with Super 44 Mufflers with polished stainless tailpipe tips designed for the GT valance.|
|17282||2 ½" with Super 44 Mufflers with turndowns for non-GT valance.|
How do you improve on a winner? Flowmaster calls it Delta Flow. Born from the Delta Force racing muffler, the new street muffler offers exciting technology that provides superior scavenging over conventional mufflers. Delta Flow technology uses additional deflectors to provide a cleaner, faster scavenging path for hot exhaust gases to virtually eliminate turbulence. Here are the benefits of Flowmaster's new Delta Flow muffler.
Resonant tuning chamber captures and cancels specific sound frequencies, which reduces resonance inside the cabin.
Power chamber creates a negative pressure (suction) that helps scavenge exhaust gases. This means more power, better low-end torque, and to some degree improved fuel economy. It also reduces exhaust system heat.
Low pressure balance chamber blocks power-robbing atmospheric pressure from adversely affecting exhaust system function.
Delta Flow Technology provides advanced noise cancellation by separating and recombining exhaust pulses at precise phase shift. In other words, quieter operation.
H-Pipe Or X-Style Crossover?
Why should you tie both sides of a dual exhaust system via a crossover pipe? Aside from how it affects sound, it is also important for performance. The crossover balances cylinder bank exhaust pulses on V-6 and V-8 engines. When you separate cylinder banks, you get a popgun sound from dual exhausts. Mixing it up allows the banks to complement one another. It also improves scavenging.
Boyd Butler of Pro Motorsports Engineering pioneered the X-style crossover-a crisscross pipe design that smoothes exhaust flow across cylinder banks. Without question, and consistently proven in stock car racing, it frees up horsepower and torque. The X-style crossover does its best work at high rpm.
Should you install an X crossover on your Mustang? If you're going racing or you like the bizarre, buzzy sound and high rpm of an X, then yes. If you're going cruising or building a show car, it's your option. The X-style crossover does improve performance, so you can expect some improvement in power.
If you're adding dual exhausts...
If you're adding dual exhausts to a Mustang that didn't come from the factory with duals, don't just drill holes in the floorpan and hang mufflers using sheetmetal screws. Use the factory hangers and stud plates, which are worth the investment. We used not only the stud plates provided by Virginia Classic Mustang, but also the electrical junction box side plates made of heavy gauge galvanized steel. Visit any home improvement store and ask for heavy gauge galvanized steel and make reinforcement plates for your floorpan, which ensures solid exhaust system hanger security.
Tailpipe positioning is tricky...
Tailpipe positioning is tricky because it mandates proper muffler positioning. If mufflers are too high or too low, you will never get the correct tailpipe angle. That's why fitment must include H-pipe, exhaust pipes, mufflers, and tailpipe before permanently anchoring anything. Ascertain proper clearance and position before welding.
These are 23-inch Flowmaster...
These are 23-inch Flowmaster Series 50 Delta Flow mufflers on a '66 Mustang. The 23-inch Flowmaster yields a tight fit. The 19-inch Flowmasters are a better fit.