Way back in the days when muscle cars were king, you never really knew how much horsepower you hand. Sometimes automakers exaggerated horsepower claims by publishing the gross numbers, sans any front accessories and running non-stock headers. Other times, to avoid higher insurance costs, they published substantially lower numbers. It was a bit of a crap shoot, one we don’t have to worry about as much these days.

Still, it is nice to know how much a particular car actually puts down at the wheels. Roush claims their 5XR makes 525 horsepower at the crank, but Muscular Mustangs found this video of John Trischler of Ray Skillman Performance putting the 5XR against the dyno test. So how did this bad boy fare?

The ten-minute video gives an in-depth look at the new Roush 5XR. This car is a replacement for the outgoing 427R, and features a Roushcharged 5.0 liter V8 engine, in addition to other enhancements like a 1g suspension and various interior and exterior upgrades. Roush claims this motor is good for 525 horsepower, but the dynometer never lies. Trischler put the 5XR to the test, and got some pretty impressive numbers. You may just want to skip to the end of the video and hear this baby on the dyno though, because it sounds sweet.

The 5XR put down 458 horsepower at the wheels, though no mention of how much torque it made. If you figure a 20% loss through the drivetrain, that works out to about 540 horsepower. If you’re more conservative and figure a 15% loss, the numbers work out to almost exactly 526 horsepower. We’d say this car is right on the money, folks. Just 150 of these will be built though, so act fast if you got the cash.