Professional Race Carburetors - Racing carburetors operate in the narrow, specialized environment of competition. This means that their whole job is focused on feeding maximum horsepower engines as efficiently as possible. For that job, the best choices are mechanical-secondary carburetors with two accelerator pumps – also known as “Double Pumper” carbs. At the same time, race engines benefit from billet metering blocks for better durability with harsh fuels and lower chance of porosity. Holley’s Professional Race carburetors generally eliminate airflow-impeding choke mechanisms, to allow maximum performance.