NASCAR announced Wednesday morning that it will change the carburetor restrictor plates on the engines to reduce speeds for Sunday's Daytona 500.
The opening of the plate will be 1/64th of an inch smaller (to 57/64ths) to greater restrict the air flow, which will give the engines about 10 to 12 less horsepower.
The change is effective immediately, starting with the first practice session Wednesday morning.
Speeds reached more than 206 mph in the Budweiser Shootout Saturday night at Daytona.
NASCAR already made two rules changes Sunday to cause the engines to heat up faster and limit some of the pairs racing that took place in the Shootout, which enabled the cars to reach higher speeds.
The front grill opening was reduced and NASCAR mandated lower radiator pressure so the engines would get hot faster. The rear car pushing the car in front could overheat in a few laps with the rule changes.
Terry Blount is a senior writer for ESPN.com.