Based on the FLEXJET NHRA Factory Stock Showdown performance numbers from the Gerber Collision and Glass Route 66 NHRA Nationals at Route 66 Raceway in Chicago, IL, the NHRA Technical Department is increasing the supercharger overdrive by changing the upper supercharger pulley for the 19-23 Chevrolet Copo 350 from 3.625 inches to 3.500 inches. This rule change will go into effect immediately. NHRA reserves the right in the future to make additional rule changes to control performance and maintain parity in the category.