Performer RPM Dual-Quad intake manifolds are designed to fit 1958-1965 Chevrolet 348/409 W big-block engines. Two versions are available, one for small-port cast iron factory heads and one for factory large port or with our Performer RPM W-series heads number 60809 or number 60819. These manifolds deliver performance with Edelbrock Performer Series or Thunder Series ABS dual-quad carburetors, and they accept our dual-quad lines, throttle linkage, and air cleaners. Includes Oil Fill Tube and matching push-in Breather. Oil Fill Tube and Breather are also available separately as number 4803. Carb center-to-center measurement is 6-7/16in.