The SLP 600HP Performance Pac for the Shelby GT500 is a surefire and easy way to add some venom to the snake's bite.
Of course, a true MM&FF evaluation wouldn't be complete with out a thorough dragstrip flogging. The GT500, which was equipped with the Powerflow exhaust system with the 4-inch tips, was driven to Old Bridge Township Raceway Park in Englishtown, New Jersey, our resident test facility. We promptly opened the hood, and while a pair of portable fans were blowing air onto the blower to cool it down, we jacked the rear end up and swapped the stock rear sneakers for a pair of 26x11.5-inch Mickey Thompson tires mounted to 17-inch Mustang GT rims. This was done due to the fact that the added power and torque would make it difficult at best to get the beast to hook upon launch.
Since this car wasn't tested in bone-stock trim, we had to look back into the MM&FF archives, where we found a best elapsed time of 12.38 seconds at 115 mph for a stock GT500. After perfecting his launch and shifting techniques, MM&FF's own Evan Smith promptly ripped off an 11.43 at 122 mph. This was with a 1.72 best 60-foot time, and on the same day MM&FF tested the new GT500KR. We have to say, the SLP-prepped GT500 held its own against the new Ford super Stang. Not too bad for some added bolt-on parts.
To install the new headers,...
To install the new headers, you will have to remove the steering column intermediate shaft and move it out of the way. This will allow you to sneak the headers in with a minimal amount of knuckle scraping, tool throwing, and cursing.
In addition to ripping it up at the dragstrip, we also took the car for a weekend to evaluate its road manners. After all, with the added horsepower, we wanted to see how tractable the car was when performing street duty. After putting on a fair amount of miles over the course of a few days, the verdict was one of happiness and, as expected, success. There was no surging when it came to the revised tune, and even though the fuel trims were changed, fuel mileage was still respectable, as we knocked down 24 mpg on the highway during one stretch. Over the course of three tanks of 93-octane pump gas, the Shelby averaged 18.5 mpg both on the highway and on roads around town. The exhaust tone emitted by the long-tube headers, x-pipe system, and exhaust system was not overly abrasive, though there was a drone at 80 mph that made us have to crank up the stereo just a bit to overcome. Overall, though, the sound and added power not only allowed the car to make a statement, but back it up. Just ask the patrons in front of a local eatery who witnessed the Shelby roll up in authority and scare a pesky 350Z into the depths of the parking lot.
The stock airbox and throttle...
The stock airbox and throttle body is also taken out to aid in installation of the headers. While the airbox is out of the car, the stock air filter was replaced with the high-flow piece that comes with the Pac.
All in all, the SLP 600HP Performance Pac for the Shelby GT500 is a surefire and easy way to add some venom to the Snake's bite. The best part of it is the fact that the parts have been tested and approved by SLP, and are all available separately from one another, just in case you don't want the whole shebang. "The advantage to the Performance Pac is that it is thoroughly tested to not only guarantee the horsepower and torque levels advertised, but it is also guaranteed to be safe for the engine for the long haul. By creating a package with components from one supplier, we know exactly how the vehicle will react, and can create a tune that comes with each package so that each package performs the same on every car, every time. This allows the customer to install the package and the tune and hit the road quickly without any worries or need for added dyno time."
While SLP has no plans to add anything to the package as of now, with how well it works and what it does for the Shelby GT500, would you really want any more? I guess by asking that question, it means we're bringing a loaded weapon to a knife fight. Let's get it on!
The pulley swap is simple...
The pulley swap is simple and easy with the proper tools. With the puller in place, we removed the stock 3.0-inch pulley, and replaced it with the new 2.70-inch pulley. The new pulley retains usage of the stock belt, so you don't have to worry about getting another rubberband for the engine.
SLP is more than happy to...
SLP is more than happy to perform the install for you in its shop, but for those do-it-yourselfers, an upper pulley installation kit will be needed to remove the press-on stock pulley. The new upper pulley measures out to 2.70 inches, and will kick the boost level up to around 12 psi.
With the Pac installed and...
With the Pac installed and the car ready to go, Daniecki strapped the beast to the dyno, got the operating temperatures up to the proper level, and laid into the loud pedal. The blower whined, the engine sang, and the tires spun the dyno rollers to an SAE-corrected rear wheel horsepower number of 601.6 rwhp at 5,700 rpm, with torque checking in at 604.4 lb-ft at 4,100 rpm. Better take out stock in your favorite tire company.
The Pac also comes with SLP's...
The Pac also comes with SLP's Powerflow-X x-pipe assembly. The new x-pipe system and high-flow catalytic converters replace the stock H-pipe and cats, reducing exhaust restriction while changing the tone to the car.
With the Pac, you have three...
With the Pac, you have three different options from which to choose when it comes to the exhaust system. SLP offers the Pac with the Loud Mouth exhaust, as well as with the PowerFlow exhaust with 3- and 4-inch tips. The Shelby GT500 we tested was equipped with the 4-inch version of the PowerFlow system.
The last piece of the 600HP...
The last piece of the 600HP Pac puzzle is the Diablo Predator programmer that is stocked with an SLP custom tune. According to SLP's Hank Daniecki, the tune takes advantage of the added boost from the smaller blower pulley with revised ignition and fuel tables. The programmer plugs into the diagnostic port, and when combined with the rest of the parts included with the Pac, makes for a simple slap it on and go kit.
To help us in getting the...
To help us in getting the Shelby to hook, we swapped the factory rolling stock for a set of 26x11.5 Mickey Thompson tires on a set of 17-inch Mustang GT rims.
With Editor Smith behind the...
With Editor Smith behind the wheel, the Shelby was hustled to an 11.43 at 122 mph. Having gotten a stock GT500 to go a 12.38 at 115, that's a 0.95-second improvement in elapsed time, while picking up 7 mph on the speed chart.
Here you can see how the SLP...
Here you can see how the SLP GT500's dyno numbers (green) compare to the stock numbers (black) the Shelby laid down before the Pac was installed. All told, the Pac is good for a solid 84 hp and 94 lb-ft of torque increase over stock.
This wouldn't be a proper...
This wouldn't be a proper evaluation if we didn't put the whip to this Pony at the track. After driving the car to Old Bridge Township Raceway Park in Englishtown, New Jersey, we cooled the blower down, swapped the rear tires, and boiled the hides in preparation for our dragstrip assault.