An 800-horsepower ProCharged Fox Mustang delivers modern performance with a classic style and vibe. When Corey Box of Box Performance rolled into the shop with a Fox configured with the familiar supercharger, Kyle Morris wasted zero time prepping the hub dyno.
Street enthusiasts frequently dream about four-digit horsepower numbers, yet balancing big boost with pump-gas drivability demands serious patience at the keyboard. Before tackling the red Mustang, the crew finished tuning a supercharged 565-inch big-block. After swapping pulleys on the truck to clear more than 1,200 horsepower on methanol, attention shifted straight to the Ford.
Under the Fox hood sits a 427-inch small-block Ford sporting Trick Flow High-Port 225 heads, a side-inlet Holley Hi-Ram intake, and a cog-driven ProCharger F1A-94. Power, controlled by a Holley Terminator X system, routes through an AOD automatic transmission to an 8.8 rearend.
Morris established conservative ignition timing and calibrated failsafe parameters to protect the engine against pressure drops. Evaluating the project’s initial targets.
“The customer that actually owns the car will be tickled pink if it makes 780 at the wheels, which I think is easily achievable,” Morris noted.
Early pulls delivered 683 horsepower before hitting the dyno speed cutoff. Adjusting the rev limit allowed the setup to produce 750 horsepower at 6,800 rpm on 13.6 pounds of boost. Reading the spark plugs revealed significant heat buildup, prompting the team to switch the ProCharged Fox to high-octane, ethanol-rich fuel.
Pouring One Ethanol R into the tank gave the motor the necessary safety margin. Morris configured the digital flex-fuel sensor tables in the Holley software, adding fuel volume and advancing timing. Swapping to a 77-tooth crank pulley and a 48-tooth blower pulley spun the supercharger significantly harder.
The combination screamed to 7,100 rpm at 16 pounds of boost, posting a peak 815 wheel horsepower.
“I was surprised it didn’t pick up more with that two degrees. We must be closer to the threshold of diminishing returns than I thought,” Morris admitted.
Manifold air temperatures skyrocketed toward 200 degrees during wide-open throttle passes, proving that pushing an 800-horsepower ProCharged Fox without an intercooler creates real thermal obstacles.
Box plans to install an intercooler over the winter to cool down incoming boost, but leaving the dyno with more than 800 tire-shredding horsepower is enough to put a massive grin on any Ford fan’s face.
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