EDELBROCK THUNDER SERIES AVS® 650 CFM, OFF-ROAD CARBURETORS - Designed and calibrated for optimum off-road performance in small-block and some big-block engines. Match with a variety of manifolds that include Edelbrock Performer, Edelbrock Performer EPS, Edelbrock Performer RPM, Edelbrock RPM Air-Gap and other brands of similar design. Includes spring-loaded needles and seats for superior fuel control in off-road terrain.