Two-time champion Tony Stewart confirmed Thursday that he has acquired half of a struggling NASCAR Sprint Cup Series team and will be a co-owner/driver starting next season. Terms were not disclosed.

The two-car team, Haas CNC Racing, will be renamed Stewart-Haas Racing in 2009.

Stewart made the announcement at Chicagoland Speedway in Joliet, Ill., site of Saturday night’s NASCAR Cup race, one day after saying he would leave Joe Gibbs Racing after this season.

The Indiana native has won 32 races and two Cup titles, in 2002 and 2005, in his 10-year career driving the No. 20 car at Gibbs. Stewart also won an Indy car title in 1997 before moving to NASCAR.

Stewart, who already owns sprint-car teams and a small race track in Ohio, said owning 50% of a NASCAR Cup team was “a once-in-a-lifetime opportunity.”

Being able to “have a new challenge and help build an organization and be part of it … is something that’s important to me,” he said.

The move also means “I can still be involved heavily in NASCAR” after his driving days are over, Stewart said. “It’s hard just to walk away from this sport.”

Haas CNC currently fields two Chevrolets: The No. 66 driven by Scott Riggs and the No. 70, which has had several drivers this year.

Despite getting their engines and chassis from the powerhouse team Hendrick Motorsports, neither car currently is in the coveted top 35 in owner points that guarantees a starting spot in the next race.

Stewart-Haas is looking at “a big list of drivers” who might pilot the team’s second car next year, along with potential new sponsors.

Ryan Newman of Penske Racing, this year’s Daytona 500 winner, is considered a strong candidate to join Stewart next season.

Many owner/drivers in NASCAR have struggled in the past, and Stewart was asked if he could buck the trend.

“There are no guarantees that this is going to be successful,” he said, but added that he hoped the team would “be competitive right away. We’re going to do everything we can to make it successful.”

 james.peltz@latimes.com