The cars driven by Jeff Gordon and Jimmie Johnson failed initial inspection and won't be allowed to practice or qualify Friday for the Nextel Cup race at Infineon Raceway.
The No. 24 and No. 48 Chevrolets had modifications to the front fenders "found to be outside NASCAR tolerances," NASCAR spokesman Ramsey Poston said. No further penalties or suspensions were announced.
Poston said the teams may repair their cars in an effort to pass inspection. Since they are prohibited from qualifying, both cars would have to start from the rear of the 43-car field in Sunday's Toyota/Save Mart 350 if they do meet inspection standards.
This is the first road race for NASCAR's new Car of Tomorrow, a bigger, bulkier and reputedly safer car that has been in development for seven years. It has run in six races this season, all on ovals.
"It's important to know that this is a Car of Tomorrow penalty," Poston said. "The inspection process and NASCAR's reaction to violations to the Car of Tomorrow violations are going to be more severe. We're going to keep this car in check.
"It's important to know that all cars in the field are starting out equal and all have the same opportunity to win as the other."
Asked why the cars could still be allowed to pass inspection and race, Poston said: "That's been our practice in the past, that we've given teams an opportunity to repair cars that have failed inspection. And we'll do the same here."
Poston said NASCAR would determine any further penalties assessed to the two Hendrick Motorsports teams after officials return to their Daytona Beach, Fla., headquarters following the race.
Dale Earnhardt Jr. was docked 100 points and crew chief Tony Eury Jr. was fined $100,000 and suspended six races after NASCAR discovered illegal brackets on the rear wing of the No. 8 COT Chevrolet last month at Darlington Raceway.
The Hendrick team's other two cars, the No. 5 of Kyle Busch and No. 25 of Casey Mears, passed initial inspection. They are built in a different shop at Hendrick Motorsports.