CHARLOTTE, N.C. — D.J. Twitty was taking it all in: the jackmen lifting the race cars, the whizzing of air guns to change tires, the slinging of 50-pound wheels. For a South Carolina native like Twitty, the loud scene was just this side of paradise.

“I’m ready to make this my home,” Twitty, 24, said. He was one of 55 recruits who attended the annual pit crew combine for Hendrick Motorsports. The auto racing team’s coaches and trainers use the all-day event in June — and a three-day minicamp held last month — to find a half-dozen athletes who can jump onto a track, gas up a car and change tires in less than 10 seconds.

Twitty, a former running back at the University of South Carolina, was in attendance because Hendrick and other teams have learned that former football players often make the best prospects for five-man crews, thanks to their strength, agility and speed. So teams scour college campuses looking for players like Twitty who didn’t catch on with an NFL team and want to trade their football helmets for fireproof suits. A few, like Twitty, know about NASCAR — he grew up rooting for driver Denny Hamlin — but most are new to the sport and can barely change their own oil.

“You don’t grow up playing pit crew in your backyard,” said Keith Flynn, Hendrick’s developmental pit crew director, who has recruited athletes for 14 years. “Most of these football guys had no idea that this is even an opportunity. But once they come on campus and see the place, they get pretty excited.”

NASCAR races can cover up to 600 miles, with cars zipping around the track approaching 200 mph. Yet races are often won by seconds, or even slivers of a second, and a slower pit stop can cost teams hundreds of thousands of dollars in prize money and potential sponsorships. Every second saved in a stop is worth about 20 car lengths on the track. Last season, the average margin of victory was 1.11 seconds.

“While you are fighting for every position on the track, you can gain multiple spots on pit road,” said Dave Alpern, president of Joe Gibbs Racing, which has about 50 athletes in its pit crews. “It can 100% win you a race and absolutely lose you a race.”

The pursuit of that edge is why Hendrick, Gibbs, Penske and other big race teams invest millions of dollars to hire and train dozens of tire changers, jackmen and gas-can carriers who can work in chaotic conditions on race days 38 weeks a year. Teams are building state-of-the-art gyms and hiring top trainers, chefs and yoga instructors. They also pay hefty salaries — some at $200,000 or more — to sign top athletes and lure pit crew talent from rivals.

Hendrick began holding its formal pit crew combine 15 years ago, and this year’s group was the largest. The athletes, who included a few college lacrosse players and wrestlers, were separated by body type: bigger linemen in one group, lankier receivers and defensive backs in another, and squatter linebackers and running backs in a third. They were evaluated on 12 skills and tasks. For several hours in scorching heat, they ran sprints, raced to put lug nuts on wheels and lifted weights at a bench press.

“If you’re a football guy, the drills are pretty similar,” said Ben Wilson, a former wide receiver at Penn State. “But the pit crew is a big learning curve because you don’t practice changing tires, and if you do, it’s rarely in 8 seconds.”