Buy now, pay later with Learn More

Need Help?

We've got you covered!

Sales & Service Hours

Sales & Service Hours

Customer Service

  • Monday to Friday: 8am - 6pm EST
  • Saturday/Sunday: Closed


  • Monday to Saturday: 8am - 5pm EST
  • Sunday: 9am - 10pm EST

Flowmaster 70 Series Big Block II Muffler 524704

Product Information
List Price:
Our Price:
5 (1 review)
Part #:
Aluminzed Steel
Inlet Style:
Dual Inlet & Outlet
Outlet Dimensions:
2.25" Inlet & Outlet
2.25" Inlet / 2.25" Outlet (Dual In - Dual Out)
  • 22" muffler
  • 5" x 10" body
  • Mild sound
  • Features three-chamber, Delta Flow Technology
  • Best suited for truck applications – quiet operation!


  • Soft, Mellow Tone: The 70 Series Big Block II muffler offers a nice soft rumble that sounds nice without being offensive. It is recommended for daily driving and towing applications.
  • Longer Case Design: The 70 Series muffler features a narrower and longer case design to work on vehicles where a 50 Big Block II muffler won't work. It is recommended for cars, trucks, SUVs, RVs, and other vehicles.
  • Delta Flow Technology: Flowmaster's Delta Flow Technology ensures unrestricted exhaust flow while providing superior sound dampening capabilities. Interior resonance is virtually eliminated for a quiet, comfortable ride.
  • Increased Fuel Economy: The longer case design of the 70 Series Big Block muffler ensures unrestricted exhaust volume for increased power and fuel mileage.
  • Aluminized Steel or Stainless Steel: The Flowmaster 70 Series Big Block mufflers are constructed of heavy duty aluminized steel or stainless steel for long lasting durability.
  • Made in the USA - Santa Rosa, CA

The 70 Series Big Block II Mufflers from Flowmaster are designed to offer increased performance while offering a deep, mild tone that won't offend the neighborhood. The 70 Series muffler is very similar in performance and tone to the 50 Series Big Block, however it uses a longer case design that works well on applications where the wider muffler won't work.

The 70 Big Block uses Flowmaster's Delta Flow technology to maximize efficiency and dampen interior resonance making it one of Flowmaster's quietest mufflers. It is designed for most cars, trucks, SUVs, & RVs with 2.5" or 3" exhaust systems. The 70 Series Big Block muffler has a case dimension of 22"L x 10" W x 5" H and a total length of 28". It is constructed of 16 gauge aluminized steel or T409 stainless steel for extended durability and life.

flowmaster-muffler-comparison.jpg (1660?003f??822)

View Available Part Numbers For This Product Line

California Residents: Prop 65 Warning

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
1  Customer Review
5 Star
4 Star
3 Star
2 Star
1 Star
Order by

Part #: FLM-524704 Posted on
Was this review helpful?
(Tarboro, NC)
Price / Value
Ease of Installation
I recently purchased a Flowmaster 70 series Big Block II Muffler from awesome site,great price and a good quality product,would recommend this site to anybody.


3 Year Warranty

Flowmaster is offering a 3 year limited warranty on the aluminum 70 Series Big Block II Mufflers.


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.