HP Main Body Retro Fit Kit for Double Pumper Carburetors Polished HolleyWant to upgrade your street carburetor to a high performance race carb, but don't have the means to do a complete carb swap? If you can turn a screwdriver, you can get increased horsepower from the new Holley Aluminum HP carburetor main bodies. These aluminum HP main body retrofit kits convert your existing carburetor to an aluminum HP main body for increased horsepower, torque, and airflow. With no air horn, choke tower, or choke control to restrict