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Flowmaster Part Number System Flowmaster muffler part numbers use a system that is far more important than just a series of consecutive numbers. From a Flowmaster muffler part number, you can determine the product series, case thickness, inlet/outlet diameters and placement, as well as any special applications. Updated - 2019-01-01

What is the difference between a 40 series and a 50 series muffler?
The 50 series mufflers are incorporates an internal resonant chamber that helps reduce interior drone in the cab area of your vehicle, and provides a slightly milder exterior tone than the 40 series. The 40 series has a more aggressive tone and sound level. It does not have a built-in resonant chamber and will generally resonate or “drone” inside the vehicle, around 1800-2000 rpm, and again around 2400-2600 rpm. So if that’s your cruising rpm at highway speeds and don’t want any drone, you may want to consider a 50, 60 or 70 performance muffler.
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What size exhaust tubing should I use for my street application?
Choosing the proper diameter of the tubing for your exhaust system is as important as selecting the right muffler. Your tubing diameter choice will affect the sound level and performance characteristics of the muffler, but keep in mind that bigger is not always better. Using tubing that is too large can actually hinder exhaust scavenging by slowing the velocity of exhaust pulses in the tubing resulting in a loss of torque. And torque is what moves the car. As a general rule, most stock to mildly modified V8 powered street applications will use 2.25” – 2.5” diameter tubing. There are many variables that need to be taken into consideration when choosing the correct tubing size for your application, such as: engine technology (flat head engines vs 60’s engines vs present day engines) cubic inch, catalytic convertors, head flow, vehicle weight, how the vehicle is driven and numerous others. Light to moderately modified street applications will generally use 2.5” and rarely some can use dual 3.00” tubing, again depending on the above named factors, sound desired etc. *We generally don’t encourage the use of dual 3” exhaust systems for just street use. Here are some guidelines for exhaust tubing size vs power that can be used for street applications: Street V8 applications – dual exhaust 2” tubing200 hp – 250 hp 2.25” tubing 250 hp – 375 hp 2.5” tubing 350 hp – 500 hp *3” tubing 500 hp – 600 hp
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Do I need to install an “H” pipe in my dual exhaust system?
Flowmaster strongly recommends using a crossover tube, otherwise known as an “H” pipe or balance pipe on all true dual exhaust systems. The crossover pipe equalizes the exhaust pressure and allows the sounds waves to communicate between both banks of the engine. Not only does this usually improve torque in the low to mid rpm range, it also creates a deeper mellower tone both inside and outside of the vehicle and helps eliminate “back-rap” on deceleration.
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Is an “X” pipe better than an “H” pipe?
Flowmaster has performed extensive testing and determined that the “H” and “X” pipes generally delivers no significant difference in performance, but does affect tone. The “X” pipe will change the sound to a higher pitched tone. Flowmaster Scavenger “X” pipes however do increase power and torque through use of their patented D-port technology and retains the deep Flowmaster muffler tone that is desired by most performance enthusiasts.
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How do I select the correct Flowmaster?
The sound of your exhaust is much like music; we all have different preferences so it’s important that the system be “tuned” to what you like. With the Flowmaster family of products we can help accomplish this by answering the questions below. This approach will allow you to choose the best product to suite your needs and expectations 1. What is the vehicle year, make, and model? 2. Which engine do you have or how much horsepower does it produce? 3. What is the vehicle used for? i.e.: daily driver, race, towing etc. 4. Preferred sound levels (interior and exterior?) 5. How are the space requirements? 6. Would you like a complete exhaust system or universal pipe kit if available? Single or dual outlet?
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What does a Flowmaster sound like?
The Flowmaster sound is unique to itself and is very different from that of glass packs or other packed style mufflers. The Flowmaster sound can best be described as a deep smooth sound and has proven to be the preferred and most recognized sound of most automotive enthusiasts. Flowmaster offers many different levels of sound from mild, to moderate, to aggressive. In general, the 60 series, 70 Series and Super 50 Series mufflers are milder with reduced interior sound. The 50 Series Delta Flows are moderate, and the 40 Series have a more aggressive tone. The Laminar Flow mufflers (Super HP2, Pro Series, DBX) provide a smooth, deep tone with minimal interior resonance. The FlowFX mufflers have a more traditional packed style muffler with a deep mellow tone.
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What is a Laminar Flow Technology Muffler?
Laminar Flow Technology mufflers are the latest generation in the Flowmaster family of performance products featuring innovative, patented technology. Flowmaster Laminar Flow Technology mufflers actually accelerate the exhaust flow as it passes through the tapered core and expands into the large volume outer core area in multiple layers. This all adds up to a design that delivers distinct torque and horsepower improvements over straight through designs, along with a deep mellow exhaust tone. See our Laminar Flow section for more information.
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Do I need to run tailpipes after the mufflers?
Yes, we recommend running a minimum of 12” tailpipe after the muffler and strongly recommend running the tailpipes out from under the car in street applications. This does two things; it directs the potentially harmful exhaust fumes away entering the drivers compartment, as well as helps minimize the sound transmitted into the cab area of the vehicle.
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How do Flowmaster Chambered and Laminar Flow mufflers compare to straight through mufflers?
Straight through mufflers are constructed using a perforated flow tube wrapped with either steel wool or fiberglass to simply absorb sound. This type of technology generally does the least in reducing sound, especially in the cab of the vehicle and cannot control drone. The packing materials can burn out fairly quickly resulting in a shortened life span and increasing sound levels both inside and outside the vehicle. The Flowmaster® designs use the sound energy to cancel itself out and not packing materials to burn out. Therefore will maintain its sound control over the life of the product. Also, Flowmaster has models that are designed to specifically reduce or remove the interior drone from most applications, if desired by the customer.
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What kind of performance gains can I expect when installing a Flowmaster system on my vehicle?
Performance gains will vary dependent upon your application. The more power the engine makes, the bigger the gains will be. Generally in full size vehicle applications, a 5-7% gain in power is fairly typical, while 1-2 mpg can be achieved. That is if you can keep your foot out of the gas to hear that Flowmaster sound.
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Will my late model vehicle run better if I replace the single inlet muffler with a true dual exhaust system?
Flowmaster does not recommend replacing factory single inlet exhaust systems with a “true dual” system on computer controlled vehicles. The computers in most late model vehicles may not be able to compensate with the fuel needed when increasing the exhaust flow, and may void your factory warranty and emission compliance. Flowmaster’s dual outlet kits will give you the look of a “true dual” system, while optimizing the vehicles performance.
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Will I lose power going from a 40 series to a 50 series, or to a 70 series?
No. Flowmaster engineers have designed each series of mufflers with maximum efficiency in mind. The differences between the various muffler series are in the varying sound levels produced both inside and outside your vehicle. This is why it is so important to take the time to carefully choose the right product that will suit your individual needs and sound preference.
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Will installing a Flowmaster Cat-back exhaust system void my vehicle’s factory warranty?
There may be some modifications that have the potential to void a vehicle’s factory warranty, but modifying the exhaust system after the catalytic converter is not one of them. All Flowmaster® exhaust systems are designed vehicle specific and do not violate manufacturers factory warranty. If you’re having problems regarding this issue, please contact www.sema.org for more information regarding consumer’s rights on performance aftermarket parts.
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How can I be sure that I’m buying a Flowmaster muffler?
The Flowmaster name is embossed in every muffler case that Flowmaster builds. If it doesn’t say Flowmaster on the case, it’s not a real Flowmaster muffler. Buyer beware; Flowmaster knock-offs may look similar, but may not perform or sound the same, and often have a high defect return rate.
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What materials are used to build Flowmaster Mufflers?
All Flowmaster® chambered products are fully MIG welded and built from either 16-gauge aluminized steel or 409 stainless steel for durability and value. Select part numbers of the 40 and 50 series are offered in 409 stainless steel (check with the tech line for updates.) The internal construction of all Laminar flow mufflers is 409 stainless steel and the dBX® line of mufflers utilizes a 304 stainless steel outer casing that can be polished to a high luster. The Super HP2 mufflers are available in either 409 stainless steel or a polishable 304 stainless steel case.
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What is “Delta Flow” technology?
This patented technology is an improvement over the original Flowmaster® design that provides improved scavenging and additional reduction of resonance inside the vehicle. This advancement was born out of Flowmaster’s extensive involvement in racing and its commitment to Research & Development. The Delta Flow design incorporates additional delta deflectors placed at precise angles, different spacing within .004-inch tolerance and in some series different sizes. The result is improved performance while maintaining a pleasant tone both inside and outside the vehicle, along with a reduction of interior resonance.
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Is stainless steel, a better material for manufacturing exhaust products than aluminized steel?
Not necessarily, it really depends on where you live geographically and the vehicle application. Through years of field testing under street and racing conditions, we’ve found in many applications, aluminized steel is just as durable as stainless steel at a slightly reduced cost. If you live where road salt can come in contact with your vehicle on a regular basis, a stainless steel muffler is the right choice. For most racing and high performance applications where daily driver chores are not common, aluminized mufflers are a great choice to consider.
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What makes Flowmaster mufflers different?
Flowmaster’s patented “chambered” design is what sets it apart from any other muffler. The theory behind the design is based on basic principles of physics. By splitting the exhaust stream (exhaust pulses & sound energy) and then recombining them in another chamber, the collision of energy cancels the sound waves, which creates a low pressure area in its place. This resulting low pressure area then helps scavenge/accelerate the following pulses into the muffler and out the tailpipe resulting in a more efficient and cleaner burn, which means more power.
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Are Flowmaster Performance Cat-back exhaust systems and mufflers street legal?
Flowmaster has fifteen different styles of performance mufflers allowing customers the opportunity to choose a FLOWMASTER signature sound ranging from mild to moderate or aggressive to accommodate the customer’s local and state laws.
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How do Flowmaster mufflers rate on a flowbench (CFM)?
Many muffler manufacturers advertise, test and rate the performance of their mufflers with the use of a flow bench. The problem with this methodology is that a flow bench produces a steady, low temperature stream of air and lacks the acoustical and thermal dynamics that are produced by an internal combustion engine. Flowmaster designs, tests, and proves its products under real world conditions in the dyno cell, at the track and on the road. After all, when was the last time you raced a flow bench?
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FAQ's

Should I use exhaust wrap on my Hooker, Flowtech or Flowmaster Headers?
If your vehicle is being run on the street or for extended periods of time, you should never wrap headers. We never recommend exhaust wraps because it insulates the exhaust too much and retains moisture. This causes the exhaust temperature to be raised to a level that fatigues the header material causing cracks and can also cause rusting and pitting due to the moisture retained. .If you choose to use an exhaust wrap, the warranty will be void. If under hood temperatures are an issue, we recommend using Hooker’s Metallic Ceramic Thermal Barrier Coating. Our coating is applied inside and out. It is corrosion and heat resistant up to 1600°F. It also reduces underhood temperatures and has a polished high luster finish. Holding exhaust temperatures inside the header increases the exhaust gas velocity producing more horsepower. You can purchase any Hooker header with our Metallic Ceramic Thermal Barrier Coating by adding a -1 to the end of the part number.
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What is the difference between your Super Competition and Competition Headers?
Hooker Super Competition headers are built from lightweight 18 gauge mild steel tubing with “tuned” lengths for maximum performance. Super Competition headers also use long transition collectors for reduced backpressure and increased exhaust flow. 5/16” machined flanges with welded O-rings make for a perfect sealing surface. Super Competition headers come with many different options in tube diameter and length for a particular application. Super Competition headers are the “World’s Best Header”. Competition Headers are built from durable 16 gauge mild steel tubing. Competition headers use long transition collectors for reduced backpressure and increased exhaust flow. 5/16” machined flanges with welded O-rings make for a perfect sealing surface. By removing some of the constraints on our designers when they design a Super Competition header, we can produce a Competition header for easier installation and a lower price. The Comp header will weigh slightly more than the Super Competition header but will last slightly longer under extreme climatic conditions. Competition headers are the “World’s Second Best Header”. We will sometimes spend two to three times more just to make a Super Competition Header work only five to ten percent better.
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What tube size do I need? Is bigger better?
Header primary tube sizes vary on many factors: engine combination, transmission type, gear ratio and intended use of the vehicle. For example a truck header will be designed using longer length and smaller diameter primary tubes to enhance low to mid-range performance, where a header for a Pro Stock race car will have larger primary tubes and large collectors for the highest flow available. Bigger generally is not better when it comes to street driven cars. when you put too large of a header or exhaust on a street driven vehicle, you usually notice a severe drop in low to mid-range performance due to a lack of backpressure. To combat this issue, Hooker sometimes builds 3 or 4 different headers for a particular application with varying tube and collector sizes.
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How thick are your flanges and are thicker flanges better?
“Not necessarily. A good flange seal can be provided through various flange thickness and tube/flange interface configurations when properly executed. Hooker header applications manufactured with a raised sealing bead are generally made with 5/16” minimum thickness flanges that are milled flat after welding to provide the designed sealing mechanism. Other header manufacturers simply run their flanges over a belt sander or body grinder, which is a far less accurate method of surfacing. Depending on the application, Hooker also builds various headers that do not use a raised-bead sealing mechanism. These applications incorporate the use of alternative construction methods that normally utilize 3/8” minimum thickness flanges, or thicker. All methods used by Hooker are designed to achieve a proper seal when installed as per the instructions.”
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Will your headers fit with aftermarket cylinder heads?
Most aftermarket cylinder head manufacturers offer stock replacement and racing heads. Hooker headers will accommodate the stock replacement head in most cases. If the aftermarket head uses an angle plug configuration, the Hooker header for that application will have footnote 62 which says that it will fit with angle plug heads. If your aftermarket head is a straight plug stock replacement, the Hooker header for your application will fit. Most aftermarket racing heads have raised exhaust ports. Most Hooker headers are designed around the stock port height and will not accommodate the raised port heads. Hooker will produce headers for raised port heads when that particular head becomes the standard (for example: Super Competition header #6225 fits 1979-93 Mustangs with the popular TFS Twisted Wedge Race Head).
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What is the benefit of a merge spear in the header collector?
A merge spear is used to prevent turbulence in the header collector by eliminating all sharp edges and pockets inside the collector to allow fast, free flow of the exhaust pulse through the header. This smooth transition also reduces the sound pressure waves for a more tuned sound.
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Will your headers fit with my other performance equipment?
In most cases, Hooker headers are developed around the stock engine location using stock equipment. Aftermarket products such as rigid motor mounts locate the motor in a different location causing possible fitment problems. Other performance products such as kickout style oil pans and performance “mini starters” can interfere with some header applications. Check the listing (read the footnotes) in our full line catalog or contact our tech department at (270)781-9741.
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