Polished PN[5420] hand-buffed for brilliant shine, designed for 1500 to 6000 RPM performance, manifold has a balanced 180+ firing order, smooth and consistent part-throttle power, makes +25 HP over Edelbrock Torker II, makes +30 ft/lbs of torque over performer, metering rods to calibrate Edelbrock PN[1405] carburetor, carburetor center-to-center dimensions = 6-7/16 in.