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Flowmaster 50 Series Big Block Mufflers

Product Information
List Price:
$253.60 - $272.94
Our Price:
$194.00 - $208.80
Made in the USA
4.7 (3 reviews)
Product Options
Select Inlet Style
  • Dual Inlet & Offset Outlet
  • Dual Inlet & Outlet
  • Offset Inlet & Outlet
Select Outlet Dimensions


    • Flowmaster's Quietest Muffler: The 50 Series Big Block muffler is Flowmaster's quietest muffler. It's designed for large trucks, SUVs, and motorhomes.
    • Ideal For Towing: The 50 Big Block muffler is ideal for towing applications. It maintains a mild tone and increased performance for better horsepower and torque.
    • Resonance Tuning Chamber: A huge tuning chamber allows for unrestricted exhaust flow while muffling the exhaust tone. This provides a mild performance tone outside the vehicle with close to stock interior sound levels.
    • Increased Fuel Economy: Flowmaster's 50 Series Big Block mufflers reduce backpressure for increased horsepower and torque. They also offer significant increases in fuel mileage.
    • Aluminized Steel: Flowmaster mufflers are constructed of heavy gauge steel that is impregnated with aluminum alloy during a molten state.
    • Made in the USA - Santa Rosa, CA

    The 50 Series Big Block muffler is Flowmaster's largest and quietest muffler, making it perfect for fullsize trucks and suvs. It is also ideal for towing applications and use on RVs, motorhomes, and other large trucks. It features a large Resonance Tuning Chamber that virtually eliminates interior drone. The Big Block mufflers large case design is designed to flow large amounts of exhaust gasses on today's big cubic inch engines, ensuring optimum performance and fuel economy. Flowmaster's Big Block muffler will give your vehicle a mild performance tone with close to stock decibel levels. The case dimensions are 22"L x 12"W x 5" H with an overall length of 28". Flowmaster mufflers are constructed of heavy duty aluminized steel and available for 2.75"-3.5" exhaust systems.

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    View Available Part Numbers For This Product Line

    Frequently Asked Questions

    What is Flowmaster's warranty?
    All Flowmaster products built of aluminized steel have a 10 year limited warranty against defective materials and workmanship. All stainless steel mufflers have a 10 year limited warranty against defective materials and workmanship.

    What is "Delta Flow" technology?
    Flowmaster's "Delta Flow" technology has evolved from extensive Research & Development at race-tracks around the country. This new technology provides superior scavenging while reducing resonance inside the vehicle. What you can expect is improved performance while maintaining a pleasant tone, both inside and outside the vehicle.

    What materials are used to build Flowmaster mufflers?
    All Flowmaster products are fully mig welded and built from 16 gauge aluminized steel for durability and value. Specific part numbers of the 40 and 50 series are also offered in 409 stainless steel, while the Hushpower II mufflers are offered in either 409 stainless steel, or 304 stainless steel.

    What pipe size should I use for a street application?
    In general, the following guidelines should be applied for street applications.

    2" tubing up to 100 hp per pipe
    2.25" tubing up to 160 hp per pipe
    2.5" tubing up to 200 hp per pipe
    3" tubing up to 300 hp per pipe 
    What is the difference between a 40 series and a 50 series muffler?
    Both mufflers have the same sound outside the vehicle, but each has varying sound levels generated inside the vehicle. The 40 series (two chamber) will resonate inside the vehicle, generally around 1800-2000 rpms and also again around 2400-2600 rpms. The 50 series (three chamber) incorporates an H-chamber that helps eliminate this interior resonance in the cab area of your vehicle.

    Will I lose power going from a 40 series to a 50 series, or to a 70 series?
    No. Flowmaster engineers each series of mufflers for very low restriction with the main differences being varying sound levels both inside, and outside your vehicle. This way you can customize your vehicles sound levels to your vehicles needs and sound preference.

    Do I need to install an "H" pipe to my dual exhaust?
    Flowmaster strongly recommends using an "H" pipe, commonly known as a "balance tube" on all "true dual" exhaust systems. An "H" pipe equalizes the pressures between both banks of the engine giving a broader and flatter torque curve throughout the rpm range. It also eliminates "back-rap" common on deceleration, and creates a deeper mellower tone both inside and outside of the vehicle.

    Is an "X" pipe better than and "H" pipe?
    Over the years, Flowmaster's testing of all types of crossovers, including "X pipes", has revealed no substantial benefits over a properly installed "H" pipe on street driven applications. However, in race applications with small cubic inch engines and /or restricted (small bore) carburetors, will respond well to the addition of X pipes, tri-y styled collectors and/or properly designed single exhaust systems.

    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 will not be able to compensate with the fuel needed with an almost doubling of the exhaust flow. Flowmasters dual outlet kits will give you the look of a "true dual" system, while optimizing the vehicles performance.

    Do I need to run tailpipes after the mufflers?
    Yes, Flowmaster highly recommends running tailpipes out from under the vehicle. This directs the exhaust fumes away from the vehicle, while minimizing the sound transmitted into the cab area of the vehicle.

    What kind of performance gains can I expect when installing Flowmasters on my vehicle?
    Performance gains will vary dependent upon your application. The more power the vehicle makes, the bigger the gains will be. Generally, a 5-7% gain of 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.

    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.


    Watch This Video
    Flowmaster Exhaust Technology Explained - Chambered Technology 101


    Product Reviews Summary

    Price / Value
    Ease of Installation
    3  Customer Reviews
    5 Star
    4 Star
    3 Star
    2 Star
    1 Star
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    Part #: FLM-530513 Posted on
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    (Tolono, IL)
    Price / Value
    Ease of Installation
    Part #: FLM-53553 Posted on
    Was this review helpful?
    (Hallettsville, TX)
    Price / Value
    Ease of Installation
    shipped in under a week. put it on my 2500 HD 6.0, fits great. took the place of factory muff. sounds great.
    Part #: FLM-530513 Posted on
    Was this review helpful?
    (Holland, TX)
    Price / Value
    Ease of Installation
    The above item purchases was an exact fit for my 04 2500HD 6.0L (box shipped indicated 99-01 8.1L however same part numbers). Shipping times were exactly as estimated on the order confirmation. There was slight damage to one of the inlet couplers (flat spot maybe caused by a drop), however an easy fix with a pair of channel locks and ball ping hammer. Overall great ordering experience.


    3 Year Warranty

    The 50 Series Big Block Mufflers are covered with a 3 year limited warranty from Flowmaster. Call 1-877-216-5446 for more information.



    Flowmaster mufflers are designed to work with new or existing exhaust systems.  They offer slip on installation and can be welded or clamped into place.  Due to the use of heavier materials, Flowmaster recommends spot welding the joints when using clamps.  On some applications it will be necessary to cut or splice when adding Flowmaster mufflers to an existing exhaust system.