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Flowmaster 70 Series Big Block II Mufflers Part #524703 Customer Reviews

Average Rating

4 Customer Reviews

A great mellow, growl and improved performance over stock

Reviewed by Thomas B (Brighton, MI) Reviewed for a 2003 GMC Sierra — Jul 11, 2010 12:20 PM

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37 of 37 people found the following review helpful.

Well, a couple of years ago I purchased two Flowmasters Super 44 mufflers to go behind my two catalytic converters. These went on my 2003 GMC Sierra 1500 HD (Crew Cab with 6' short bed) 6.0L V8. I was excited since I would have true duals and the loudest mufflers that Flowmaster made. They sounded like a hot rod on the outside and the inside resonance and noise was terrible, especially around 25 mph and 75 mph (horrible roaring/annoying sound). After a year, I had to get rid of them and put my stock back on. I needed something aftermarket, but wanted a deep mellow tone with good low end power for my truck. Behold, the 70 series big block II. A great sounding muffler that lets you know you have a powerful muffler, but not annoying in the least bit. The inside resonance is not even there - a low mellow sound when you hit the gas pedal and then it disappears when you cruise at 20, 30, 40, 50, 60, you get the picture. A great muffler for the person who uses their truck, suv, etc for everyday use, work, towing, family activities, etc. If you're looking for something crazy loud, inside cab and out, go with something else (a friend told me that even the 50 series big block is a little too loud for this truck, if you looking for low and mellow). But if you're looking for a mild, good strong, a little throaty sound with increased torque and towing power, this 70 series big block II muffler is for you. Check out the reviews and videos online. Hope this review helps you out.

Much Better then stock!!!

Reviewed by Poria A (Houston, TX) Reviewed for a 2007 Toyota Tundra — Nov 19, 2009 4:12 PM

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12 of 13 people found the following review helpful.

I bought the FM 70 series big block 2 bc it was the only one that would fit my stock pipes. I doubted the muffler at first because i heard its not a big sound but when i had it installed it made a aggressive sound. Not too much but enough to hear a good rumble when you accelerate. I would recommend this to people who want a more of a rumble but enough to give you a headache

Paul in Sherwood, OR

Reviewed by Paul G (Sherwood, OR) Reviewed for a 2002 Chevy Express — Oct 14, 2008 10:12 PM

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7 of 7 people found the following review helpful.

The tech support rep recommended this muffler for my one ton Chevy Van. It was a perfect fit, the muffler shop I chose had no trouble installing it. They made a new full 3" tailpipe to match the muffler output. It's nice to be able to hear the engine running now, the noise inside is audible but not too loud. The sound outside is best described as muscular & throaty. Great sound. It is too early to tell if my gas mileage has improved or how it performs pulling my RV trailer. I also added a K&N air filter.

Perfect for Explorers

Reviewed by Igor K (Kirkland, WA) Reviewed for a 1999 Ford Explorer — May 24, 2007 10:47 AM

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10 of 11 people found the following review helpful.

I have an explorer V6 SOHC. After installation I got: 1. Better performance and improved MPG 2. Deep but not too loud sound, I was afraid that X will sound like a Civic.

Flowmaster 70 Series Big Block II Mufflers - 524703

Dual Inlet / Center Outlet
  • $165.42 - $170.60
  • 1-Year Lower-Price Guarantee
  • Free Shipping
  • Ships Between 3/29 - 4/02


  • Part Size:
    2.25" inlet/3" outlet
  • Style:
  • Part #:
  • Flowmaster Part #: 524703
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