Proflow's Duel Air intake manifold is designed for street 253-304-308 c.i.d. Holden ,or Commodore V8 engines. This intake manifold is a dual-plane design that is tuned for excellent throttle response from idle to 5500 rpm. Designed to fit both cylinder head bolt hole patterns. Pilot holes have been drilled on each side of the exhaust crossover for early or late model cylinder heads and will need to be drilled out depending on application. Accepts both square-bore and spread-bore carbs. Fits Red/Blue/Black engines. Does not have a provision for external heat crossover. These are avalable in Natraul or black powder coated cast-Aluminium.