DAYTONA BEACH, Fla. (AP) - Chip Ganassi Racing typically goes into the Rolex 24 at Daytona as the heavy favorite.
Not this weekend.
Ganassi switched to Ford during the offseason, and a variety of issues have raised questions about the competitiveness of the two-car entry for the twice-around-the-clock endurance race that begins Saturday.
A rule change ordered by IMSA cost Ford valuable horsepower and drivers have complained they are down as much as 5 mph on the straightaway compared to the Corvettes. They've also said there's a design flaw in their splitter that's created a downforce disadvantage through the road course portion of Daytona International Speedway.
''It's a big change for the team,'' said Scott Dixon, the reigning IndyCar champion and lead driver of the No. 02 Riley DP. ''Aerodynamically, it's a big task. With the new engine and an engine that really hasn't done a 24-hour race before, and being turbo, there's lots of different areas that you can improve and make it better.
''Right now it's just trying to make the process as quick and as smooth as possible, but also trying to get the most out of it too. It's going to be a tough race for us, but obviously when you team up for the first time you've got lots to learn.''
Ford, in the Tudor United SportsCar Championship as a factory program with a production engine that is 70 percent common to the Taurus SHO, is debuting its new EcoBoost engine package this weekend. Any time a manufacturer debuts a new element to its program it runs the risk of reliability issues, and problems to the 3.5-liter V6 twin-turbo could ruin the race for both Ganassi and 2012 winner Michael Shank Racing.
But Jamie Allison, director of Ford Racing, said any reliability questions Ford had in preseason testing were exhaust related. He's confident the engines can survive the race because Ford ran them the equivalent of four 24 Hours of Daytona on the engine dynamometer, a distance of 11,000 miles.
''This is what you do when you bring something new to racing,'' Allison said, acknowledging a disparity between Ford and Chevrolet that came after IMSA ordered engine restrictions following preseason testing.
''It is a 24-hour race and we believe that just with the series adjustments, to just make sure it's more consistent like the (test) was, then we'll be able to be in contention with the right strategy, with the right circumstance, and with the right combination of fuel mileage and power, which is what EcoBoost is all about, and the right teams, present itself to potentially win the race.''
John Maddox of Roush Yates Engines said after two years of preparations, Ford has ''pulled some Hail Mary's in the last three weeks'' to pass its final durability test earlier this week.
''We feel really good about the engines we put in the cars,'' he said. ''We're going to run the race conservative. We're not looking for just great fuel economy, we're not looking for just great speed. We're looking to finish the race and be racing at the end.''
Ganassi is the most successful team in Daytona Prototype history. It won its seventh DP team championship using BMW engines last season in Grand-AM - before Grand-Am and American Le Mans merged to create United SportsCar - and goes into Saturday's race with two new lineups.
Dixon is teamed with Indianapolis 500 winner Tony Kanaan, Marino Franchitti, who took older brother Dario's spot after Dario was forced to retire following his October crash at Houston, and Rolex rookie Kyle Larson.
Scott Pruett, who last year tied Hurley Haywood's mark of five overall Rolex victories, is teamed with regular co-driver Memo Rojas. But gone from last year's winning lineup is Juan Pablo Montoya, replaced by Jamie McMurray and newcomer Sage Karam, the Indy Lights champion who will be racing a car with fenders for the first time.
But Pruett is thrilled for his first race back in the blue oval camp: He started with Ford in 1985 and was signed as a full-time factory driver the next season. Pruett won four IMSA and SCCA Trans-Am championships in three years before moving to IndyCar racing.
Both of Pruett's IndyCar wins came with Ford and his one full season in the NASCAR Sprint Cup Series was with Ford.
''We've spent so many years together and had so many victories together and also, this is just a brand new adventure,'' Pruett said. ''I think sometimes people just think of Ganassi just coming on and jumping back on and immediately being the fastest, the top, the everything, and I'm excited because this is so new. This is a brand-new technology with the EcoBoost V-6 twin-turbo, there's a lot of changes with that, and sometimes you need to take a little step back to step forward.
''Realistically, I think we're excited to get into the race, excited to be here and kick off the season.''