6227HD Single-Plane Aluminum Intake Manifold

The Offenhauser 6227HD Intake Manifold provides a high-performance solution for Ford 240 and 300 inline-six engines, specifically configured for vehicles utilizing headers. By eliminating the heat crossover and riser provisions found on standard manifolds, this heat-delete design reduces unnecessary intake heat and provides significantly improved clearance for header installations. It functions as a performance-oriented C-Series manifold that bridges the gap between factory stock and dedicated racing setups. Technically, the manifold is constructed from aluminum and is optimized to deliver consistent airflow, with potential gains of up to 70 horsepower on stock engines when paired with appropriate camshaft and tuning upgrades. It utilizes a square-flange mounting pattern compatible with Carter or Holley 4-barrel carburetors sized 500 CFM or larger. While physically compatible with most cylinder heads through the late 1980s and early 1990s, minor adjustments to linkage or water passage plugs may be necessary for engines newer than 1981. Installation requires careful attention to header selection and hardware. Hedman headers are strongly recommended for optimal fit, while Hooker headers are generally compatible. However, Clifford headers are not recommended as they are designed specifically for Clifford intakes, and Borla headers do not fit due to clearance issues. Users should employ proper header installation kits, including spacers and clamps, especially on engines from 1981 or later. A Remflex Header Gasket (#3005) is the recommended sealing solution.