Designed for 330-350-403 c.i.d. Oldsmobiles and 1980-1/2 to 1985 307 c.i.d. engines with 5A heads (casting #3317). The Performer RPM Olds manifold is a high-rise, dual-plane design with 180° firing order engineered for maximum top-end horsepower while maintaining throttle response. Port flange has extra material above the runner for use with cast iron 455 heads and Edelbrock Performer RPM heads #60519. Has clearance for HEI distributor. Carb pad accepts square-bore carbs without adapters.