Edelbrock part #75641 RPM Air-Gap 351C intake manifold design utilizes the same race-winning technology that's been used on Edelbrock's Victor Series competition intakes for many decades. Designed to improve performance on the street or racetrack, this manifold features an open space that separates the runners from the hot engine oil resulting in a cooler, denser charge. The RPM Air-Gap manifold for 351 Cleveland engines is designed to complement Edelbrock's 351C Performer RPM cylinder heads #61609, #61629, #61625 and also works well with 4V and 2V cast iron Cleveland heads.