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Flowmaster Original 40 Series Offset Muffler - 2.5 in. (79-04 All, Excludes 99-04 Cobra)

35 Reviews
Our Price

$81.32

  • Item #18401
  • MPN #42543
  • Market Price $90.99
  • You Save 11% ($9.67)
In Stock Ships same business day.
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Product Videos Customer Photos
Features
  • Signature Flowmaster Sound
  • Original Two Chamber Technology
  • Offset inlet and outlet design
  • 2.5" inlet/outlet diameter
  • Aluminized Steel Construction
  • Sold Individually
Description
That Flowmaster Sound. Improve your Mustangs exhaust flow for an increase in horsepower and a deeper throatier exhaust note with a set of Flowmaster 40 Series Mufflers for a truly classic muscle car sound. Superior Design. The Flowmaster 40 Series Mufflers are MIG welded from durable 16 gauge aluminized steel for durability and value. The 40 series mufflers use Flowmasters original two chamber design to increase power and sound. And each muffler is embossed with the "Flowmaster" name so you know it is the real article.

Application. The 40 Series Muffler's outer case measures 4" x 9.75" x 13", and features a 2.5" diameter inlet and outlet in an offset configuration. This is the perfect muffler for the 1979 to 2004 Mustangs. Excludes 1999-2004 SVT Cobra.

Mustang Fitment: 1979 1980 1981 1982 1983 1984 1985 1986 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 Details

What's in the Box
  • (1) Muffler
Installation Info

Installation Time: (approx) 2 Hours

Difficulty Level:Advanced mechanical skills required.

Tech Specs
40 Series Delta Flow versus 40 Series Original versus Super Flow 44 Series
  • Minimizes interior resonance
  • Aggressive exterior tone
  • Two Chambered Muffler
  • Made of Aluminized Steel
  • No minimization of interior resonance
  • Aggressive tone inside and out
  • Two Chambered Muffler
  • Made of Aluminized Steel
  • Delta Flow technology minimizes interior resonance
  • Aggressive deep powerful tone
  • Two Chambered Muffler
  • Made of Black Aluminized Steel
Fitment
  • Bullitt - 01
  • Foxbody - 79, 80, 81, 82, 83, 84, 85, 86, 87, 88, 89, 90, 91, 92, 93
  • Mach 1 - 03, 04
  • V6 - 94, 95, 96, 97, 98, 99, 00, 01, 02, 03, 04
  • Cobra - 94, 95, 96, 97, 98
  • GT - 94, 95, 96, 97, 98, 99, 00, 01, 02, 03, 04

Most Helpful Reviews View All

Overall Rating 4.8/5 Write a Review
5/5
Takes some time

I had 44's on but nowhere near the same sound as the original flow 40 series...going through tunnell's is heaven and shifting at 2500 rpms is heaven sent lol they were a tad quiet at first but after 100

Read More
Helpful (38) (3)

5/5
Classic 40s

I had these welded in today they sound incredible I have the stock h pipe with cats and it is still nice n loud, it has a great deep tone and it was a great 1st mod for my car. 2200 RPM is the sweet s

Read More
Helpful (24) (2)

Videos

Customer Photos (6) View All

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Q & A (3 Questions, 6 Answers) Ask a Question

install when installing these do the existing short pipe piece on the muffler go over the stock pipes on the car? And can you use exhaust clamps instead of welding as a temp job?

Arthur Year: 1998 Model: GT

Question Resolved
Good Question (0) (0)
  • I actually welded these on my car 3.5 years ago, and unfortunately do not remember for sure, but I think welding them is the only option.

    Helpful (0) (0)

    MineralGreyGT Year: 2002 Model: GT

    Top 10 Contributor

Show 1 more answer

2? Im new to the whole muffler system my cobra has one and it sounds nice. My fiance has an 04 gt and im going to get her this one but do i need to buy 2? or just 1 all help appreciated

forty Year: 2004 Model: GT

Question Resolved
Good Question (0) (0)
  • You will need two as the car has two mufflers.

    Helpful (1) (0)

    Best Answer

    MineralGreyGT Year: 2002 Model: GT

    Top 10 Contributor

Show 1 more answer

2001 v6 Mustang So if I replaced my Muffler with the Flowmaster 40s, Would my exhaust have a deeper tone? I still have all stock underneath the car. I do have CAI though. Pretty much Stock shorties, stock y pipe and so fourth. Thanks!

XSlashDashX Year: 2001 Model: V6

Question Resolved
Good Question (0) (0)
  • Yes. Changing the mufflers will change the cars exhaust note.

    Helpful (0) (0)

    MineralGreyGT Year: 2002 Model: GT

    Top 10 Contributor

Show 1 more answer

Reviews (35) Write a Review

  • 5 Stars .86 86%
  • 4 Stars .11 11%
  • 3 Stars .03 3%
  • 2 Stars 0 0%
  • 1 Stars 0 0%
4.8

out of 5 stars

35 Customers Recommend this Product

Installation Time:Full Day

Installation Cost:$100-$250

  • Loudness / Volume: 3.866667 3.9/5
  • Exhaust Note: 4.4 4.4/5
  • Fit & Finish: 4.6 4.6/5
  • Bang For Your Buck: 4.6 4.6/5
Filter By Sort By
  • 5/5

    Takes some time

    July 10, 2010

    I had 44's on but nowhere near the same sound as the original flow 40 series...going through tunnell's is heaven and shifting at 2500 rpms is heaven sent lol they were a tad quiet at first but after 100 miles there starting to wake up!! dont get any but the original flows!!

    Co

    Helpful (38) (3)

  • 5/5

    Classic 40s

    April 05, 2010

    I had these welded in today they sound incredible I have the stock h pipe with cats and it is still nice n loud, it has a great deep tone and it was a great 1st mod for my car. 2200 RPM is the sweet spot.

    Dale P

    Helpful (24) (2)

  • 5/5

    great mufflers

    February 25, 2010

    I put on a pair of Flowmasters and what a difference they made in sound and horsepower. Getting these mufflers along with a cold air intake and your mustang will improve performance 100%. I recommend these mufflers to other mustang owners.

    Chris

    Helpful (22) (2)

  • 5/5

    Great sound

    August 27, 2010

    Installed Original 40 Flowmasters and am very please with the sound. The only problem I had was I had to adapt the flanges to my orginal equipment pipes. Be sure you know what size pipes you have before ordering.

    Bob

    Helpful (18) (1)

  • 5/5

    nice

    October 06, 2009

    Very nice product, Adds the nice deep throaty exhaust note

    C

    Helpful (10) (2)

  • 5/5

    Folwmaster 40

    November 17, 2010

    sound great. one of the best mufflers ive had. Make my mustang sound like a gt. =]

    Michael Jaser

    Driving Style: Daily Driver

    Helpful (5) (1)

  • 5/5

    97 v6 mustang

    August 17, 2010

    i have 2.25 pipes to 2.5mufflers to 2.25 tips. it has no h or x pipe and it sounds good at low rpms get a little raspy at high rpms. i was worried at first but the sound is great with a bbk throttle body and k and n cai. i would recommend them to other v6 owners. the were also a great price and the shipping is free and fast

    jon

    Year: 1997 Model: V6

    Helpful (6) (2)

  • 5/5

    Can't beat the classic note of these 40 series mufflers

    January 01, 2014

    I bought these to replace a set of awful sounding mufflers the original owner of my cobra installed. I'm very happy with the classic note of these mufflers. I am very happy to see the quality of flowmaster remains the same it was back in the 90's! I also commend American Muscle for their customer service. There was a small issue over shipping but customer service was quick to communicate and solved the problem fairly and swiftly.

    Jeremy88

    Year: 1997 Model: Cobra Driving Style: Street / Strip 'Stangs I have owned: 5+ Florida

    Helpful (2) (0)

  • 5/5

    Great sound

    March 05, 2010

    I have Original 40 series on my '01 V6 model and to my ears it is a great sound. People ask me a lot if it is the GT model, and one GT owner told me, "That sounds amazing for a V6!" It doesn't get too raspy like some other kits might. Overall a great choice.

    Daniel C

    Year: 2001 Model: V6

    Helpful (7) (4)

  • 5/5

    Sound Awesome

    October 10, 2011

    Replaced old mufflers once they started to rust at the inlet pipe, these new mufflers sound amazing on my dual exhaust V6.

    Top 100 Contributor

    SonicEvan

    Year: 2004 Model: V6 Driving Style: Daily Driver 'Stangs I have owned: 1 Lethbridge, AB, Canada

    Helpful (3) (1)

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