Edelbrock RPM Air-Gap 2-O Intake Manifold for Chevrolet 396-502 Big-Block V8Edelbrock part #7561 RPM Air Gap 2 O intake manifold is designed for street 396 502 c. i. d. Chevy V8's with large oval port cylinder heads (1975 and earlier) or Edelbrock Performer Performer RPM heads. This RPM Air Gap incorporates the same race winning technology that's been used on our Victor Series competition intakes for decades. The Air Gap design features an open air space that separates the runners from the hot engine oil resulting in a