Action Express Racing, Jack Aitken and Earl Bamber are firmly in the drivers seat going into the second half of the WeatherTech SportsCar Championship.

The No. 31 Cadillac Whelen V-Series.R team headlined a double GM victory at Detroit, with García and Sims winning GTD Pro in their No. 3 Corvette Racing by Pratt Miller Motorsports Z06 GT3.R.

Cadillac Whelen and Corvette Racing remain the teams to beat in practice for the IMSA Chevrolet Sports Car Classic in Detroit, to the delight of the GM representatives in front of their worldwide headquarters.

Despite a penalty and a nose change, the team's two factory 963s ran in formation hour after hour and went on to deliver a 1-2 finish.

It’s a 1-2 for Roger Penske’s Porsche factory team, with the No. 7 963 leading the sister No. 6. The gap between the two is under two seconds, and the margin to third is a reasonably comfortable seven seconds.

The No. 31 Cadillac Whelen V-Series.R has led from the drop of the green flag to the end of the first hour of the race.

Cadillac has won five of the last nine editions of the Mobil 1 Twelve Hours of Sebring, including the first race of the current GTP era in 2023, and appears best suited to disrupt Porsche’s grip on IMSA’s top class.

Porsche Penske Motorsport's throwback-liveried 963s set the pace at the 12 Hours of Sebring weekend got underway.

Porsche Penske Motorsport may have won each of the last three IMSA Endurance Cup races in the Sunshine State, but achieving a clean sweep of the so-called 'Florida 36 Hours' two years in a row will be a tough task.

Felipe Nasr held off Jack Aitken and Cadillac Whelen to take Porsche Penske to a third straight victory in the Rolex 24.