Designed to improve performance on the street or racetrack, the RPM Air-Gap 351 Cleveland manifold features an open space that separates the runners from the hot engine oil resulting in a cooler, denser charge. The Edelbrock air-gap design utilises the same race-winning technology that's been used on Edelbrock's Victor Series competition intakes for many years. The RPM Air-Gap manifold for 351 Cleveland engines is designed to complement Edelbrock's new 351-C Performer RPM cylinder heads # ED61609, # ED61629 and also works well with 4V and 2V cast iron Cleveland heads. Made in USA