Ford 240-300 6 Cylinder Dual Port Manifold. Through 1981. The Dual Port and “C” Series accept the Carter or Holley STD bore 4bbl carb. Carb size recommended for DP is from 390 CFM to 500 CFM; for “C” Series 500 CFM and larger. Use Holley No 8007 (390 CFM), Carter No 9400, or Carter No 9500 on Dual Port – Remove kick-down arm for linkage clearance. Carbs clear “C” Series manifold without mod. Offy universal linkage accessory kit is recommended in most installations. These manifolds on a stock 240-300 C.I. engine can increase HP output by 50 HP! Dyno tests on a Ford six with Dual Port manifold, headers and cam produced as much as 115 HP over the stocker!