From Factory X to IHRA Bratz: Holbrook Family Converts S650 Mustang To Twin Turbos

The old saying goes, “When one door closes, another opens,” and that’s exactly how Del Holbrook is approaching his transition to the IHRA Bratz series. Holbrook has taken over the driving duties of his father’s former Factory X S650 Mustang and is now trying his hand at 28×10.5 small-tire racing.

Originally, Jerry Bickel Race Cars built the Mustang for Chris Holbrook, Del’s father, to compete in NHRA’s Factory X class. When the Factory X class was discontinued, the Holbrook family needed to find a new place to race their slick S650. The IHRA Bratz class ultimately got the gears turning in the shop.

“We saw the new Bratz class with IHRA and thought it would be a bit of a change for the crew and me, and also a pretty cool experience to race with some of the legends from the small tire and street outlaw world,” Holbrook says. “We discussed making the switch to IHRA with Ford Racing, and they were excited about it, so we converted the car over for the IHRA small tire Bratz series.”

The Mustang is powered by a Holbrook Racing Engines-built 327 cubic-inch Coyote, based on a Ford Racing Werewolf block and topped with a set of Ford GT500 cylinder heads. Behind the engine is an M&M Transmissions TH400 paired with a bolt-together torque converter.

When the Mustang competed in Factory X trim, the engine relied on a Whipple supercharger for boost. For its IHRA Bratz configuration, the team wanted to take a different approach.

“We decided to go the twin-turbo route because it’s a setup we’ve been wanting to try for a while, and we don’t have to worry about snapping the crank snout as we have with superchargers in the past,” Holbrook explains. “The turbo setup uses Precision Turbo 86/85 units with Turbosmart wastegates and blow-off valves. The turbo kit plumbing and welding were done by Nick, Zach, and Wayne Prysdale from ZWN Performance. The team did awesome work in a very short amount of time.”

Now that the turbo conversion is complete, the goal for Holbrook’s team is to jump right into the mix with the heavy hitters in the class. That’s especially impressive considering the combination uses a block and cylinder heads that can be ordered directly from Ford Racing.