In NASCAR, restrictor plates are placed between the carburetor and the intake manifold to restrict the ammount of air/fuel mixture that can enter the engine. This reduces the horsepower the engine can create and therefore slows the racecar down. Used at Daytona and Talladega.
A thin metal plate with four holes that restricts air flow to the engine, reducing the horsepower. Used at Daytona and Talladega.
An aluminum plate that is placed between the base of the carburetor and the engine's intake manifold with four holes drilled in it. The plate is designed to reduce the flow of air and fuel into the engine's combustion chamber, thereby decreasing horsepower and speed.