For the 2011 model year, Ford produced 5,100 units of the Shelby GT500. Just 126 of those examples had a glass roof option and finding one for sale these days isn’t an easy job. And even if you find a glass roof GT500 from that model year, it will cost a little fortune to purchase it. Someone recently bought one of those 126 cars with around 83,000 miles on the clocks and wanted to check how much power the engine produced in its current condition.

In a completely stock form, the 2011 Shelby GT500 generates 550 horsepower and 515 pound-feet of torque at the flywheel. As a reminder, 2011 brought a new aluminum 5.4-liter V8 engine for the performance pony, which was around 100 pounds (45 kilograms) lighter than the previous cast-iron engine. Thanks to substantial upgrades, the motor was not only more powerful but also more efficient, eliminating the US Gaz Guzzler Tax for the sports car.

This particular car isn’t exactly stock, though. A new cold air intake system, a new VMP heat exchanger, and an upgraded Borla exhaust system make it easier for the supercharged engine to breathe. The car from the video at the top of this page has a tank full of 93-octane fuel. The TR-6060 six-speed transmission is completely stock and the dyno runs are performed in fourth gear, which has a 1:1 ratio.

The best result this red 2011 Shelby GT500 (which still lacks its original stripes but those will be added soon) registers is 508 hp at the wheels. If we account for an average 15-percent drivetrain loss, this would mean the peak output at the flywheel is around 584 hp, which is a pretty decent result considering the mileage and the relatively small tweaks to the engine. Torque-wise, 484 lb-ft at the wheels should mean approximately 557 lb-ft at the engine, again considerably more than the factory numbers.

While a dyno run isn’t the only (and most accurate) way of judging an engine’s overall condition, we could say this 5.4-liter supercharged V8 is rather healthy.

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