GT350 Growl
Lethal Performance upgrades its Shelby with a Magnaflow cat-back and more
By Steve Turner
Photos by Steve Turner and courtesy of Magnaflow
Born with an dual-mode exhaust from the factory, the Shelby GT350 is already one of the best sounding Mustangs ever built. That’s especially true of the R-model, which doesn’t wear resonators before the mufflers like the standard Shelby does. But it could always sound better, right?
Lethal Performance has already taken its GT350 project over 800 rear-wheel horsepower with the addition of a Whipple 2.9-liter supercharger, but that was with the factory cat-back exhaust in place. To free up some exhaust flow and rev up the car’s auditory personality, the company chose to upgrade the exhaust with Magnaflow’s cat-back system (PN MAG-19283).
“Even before Lethal Performance was created I’ve always been a huge fan of Magnaflow. My first Mustang ever was equipped with one of their systems. Not only did I love the way it sounded, but the fitment and quality of their system was awesome,” Jared explained. “So once we got into modding Mustang after Mustang it was a no-brainer to stick with the Magnaflow brand. Not once have we ever not liked how their systems sounded on our cars or thought about switching it for something else. So when it came to our GT350 it was a simple choice to go Magnaflow once again.”
Not only do the Magnaflow cat-back systems lack resonators, they are built from 3-inch, mandrel-bent, 409 stainless steel pipes. They feature an integral X-pipe crossover and route exhaust out to a pair of Magnaflow’s Shelby-specific Competition mufflers. These quad-tip cans are unique to the Shelby as they are equipped with valves just like the factory mufflers, so they accept the factory electric motors for compatibility with the GT350’s two exhaust modes.
To see how this system goes on we met up with the Lethal GT350 at Power by the Hour in Boynton Beach, Florida. There, Jake Long removed the stock cat-back exhaust and bolted on the Magnaflow. The result was an even more aggressive exhaust tone even with the factory catalytic converters in place. Listen to how the system sounds with the stock cats and Lethal’s cat-delete race pipes in this video…
[video=youtube;0KjhCDI8_WI]https://www.youtube.com/watch?v=0KjhCDI8_WI[/video]
For more of what the system sounds like you can check out these clips...
[video=youtube;Vak5jk7zAhU]https://www.youtube.com/watch?v=Vak5jk7zAhU[/video]
“The Magnaflow system sounds awesome. Even though we put the stock catted mid-pipes on the car for our initial testing their system still offered a deep throaty sound with no rasp whatsoever,” Jared said. “I also didn't notice any drone on the drive home on the highway. We’re really looking forward to ditching the cats again and eventually hearing the system with an off-road long-tube header setup.”
While the exhaust system was out of the way, it was also a convenient time to install a prototype carbon-fiber driveshaft from The DriveShaft Shop along with a driveshaft safety loop from BMR Suspension.
After this round of upgrades, it’s time for a couple more mods before the Lethal GT350 returns to the local racetracks.
“Next up for our GT350 is a bad-ass long-tube header setup from our friends at Kooks custom headers followed by a new RXT twin-disc clutch from McLeod Racing,” Jared added. “Then it's time to hit the drag strip and road course and see what this beast can do!”
Built from 3-inch stainless steel tubing, Magnaflow’s new cat-back exhaust for the 2015+ Shelby GT350 (PN MAG-19283) features an integral X-pipe crossover and a set of the company’s Competition mufflers specially designed for compatibility with the Shelby’s factory exhaust modes. It is the first system to offer such a feature for the GT350. Lethal Performance opted to install the system with the stainless steel tips seen here, but there is also a version with carbon-fiber tips (PN MAG-19299)!
Get down to business by disconnecting the battery and safely raising the vehicle on a lift or jackstands. Then disconnect the electrical connectors for the valves in the factory mufflers. Then you can loosen the factory band clamps joining the factory cat pipes to the cat-back.
With the clamps loose, you are ready to remove the fasteners on the exhaust hangers. Be sure to have someone help you wrestle on the factory exhaust before you free the fasteners completely. Angle the front of the exhaust down and forward as you slide it out of the rear valance.
With the factory exhaust on the ground you can remove the electric motors that actuate the valves inside the factory mufflers. In closed mode only two of the stock exhaust tips are open, but when the switched manually into open mode or as part of one of the more aggressive driving modes, the valves unleashes flow through all four tips. You will transfer these motors to the Magnaflow system so it will function just like the stock system.
Here’s a comparison of the stock cat-back and the new Magnaflow system. With its larger diameter, lack of resonators and freer-flowing mufflers the Magnaflow system already looks like a winner. Add in that it retains the dual-mode muffler functionality and it seems a bit lighter and looks like a great upgrade for the GT350 crowd.
One wrinkle of the Magnaflow install is that the new mufflers feature integral tips, while the stock mufflers outlets are divorced from the valance-mounted tips to allow for cooling during long track sessions. That means removing the stock tips from the valance to make room for the new exhaust.
Using new hardware, swap the factory electric motors onto the mounting pedestals on the Magnaflow Competition mufflers. Be sure to engage the alignment springs of the stock motors into the keyway slot of the new valve before you bolt them down.
Before installing the exhaust system it was an opportune time to swap out the factory two-piece driveshaft in favor of a prototype, one-piece carbon fiber ’shaft from The DriveShaft Shop. Jake started by installing this adapter.
The driveshaft swap is a simple remove and replace operation, and Jake slips the shaft onto the transmission and hand-tightens the fasters before raising up the rear of the shaft and bolting it to the diff adapter.
Jake wraps up the driveshaft install by torquing the fasteners to 57 lb-ft of torque.
With the new driveshaft in, Lethal opted to also install one of BMR Suspension’s driveshaft safety loops (PN BMR-DSL017H; $119.95). Jake first secured the hammertone-coated mount to the factory transmission crossmember.
After orienting the loop with the mounting holes on the mount, Jake bolted up the loop.
Back to the Magnaflow install, Jake slipped the X-pipe into the factory clamps and snugged the clamps to the factory cat-pipes. You don’t want to final tighten the system until you ensure everything is properly oriented and clearanced.
Oh, and one more important step before you drive the car with the new D.S.S. carbon fiber driveshaft. You must measure the metal tubing between the carbon shaft and the mount to ensure it is between 3 ¼ and 3 ¾ inches. If it isn’t and you run the car you’ll give up your warranty on the driveshaft. This one clocked in right at 3 ¾.
Jake then clamped the under axle pipe to the X-pipe and slithered the Competition mufflers into place before loosely clamping the whole system in place.
After adjusting the system for proper orientation of the exhaust tips in the valance, Jake tightened all the clamps for good. After you drive the car for 50 miles or so, you’ll want to get back under the car and double-check the tightness of the fasteners on all the clamps to ensure the heat cycling hasn’t loosened things up.
Here’s the finished install and it sounded great even with the factory cats in place. Jake reinstalled those before installing the new cat-back so Team Lethal could document the sound of the Magnaflow system with the stock cats and the Lethal cat-delete race pipes.
