CHEVROLET 348/409 W-SERIES V8 PERFORMER RPM DUAL-QUAD (1500-6500 rpm) Performer RPM Dual-Quad intake manifolds are designed to fit 1958-1965 Chevrolet 348/409 "W" Series 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 #60809 or #60819. These manifolds deliver performance improvements in the 1500-6500 rpm range with Edelbrock Performer Series or Thunder Series AVS dual-quad carburetors, and they accept our dual-quad accessories including fuel lines, throttle linkage, and air cleaners. Includes Oil Fill Tube (not installed) and matching push-in Breather. The Oil Fill Tube and Breather are also available separately as #4803. Carb center-to-center measurement is 6-7/16".