Engine Intake ManifoldEdelbrock part #7520 Air Gap Dual Quad O intake manifold is designed for street 396 502 c. i. d. Chevy V8's with 1975 & earlier oval port heads. This intake stands 7 8" taller than the low profile C 66 O dual quad intake and offer performance improvements in the 1500 6500 rpm range. The large runners feature our unique Air Gap design that separates the runners from the hot engine valley for a cooler, denser charge.