The Offenhauser 6227C-HD is the go-to 4-barrel intake for building power on a Ford 240 or 300 inline six. It's the same C-Series aluminum manifold as the standard 6227C, but without the heat riser and its bolt holes, giving you a cleaner manifold for performance builds.

Why upgrade: The factory 1-barrel intake is the biggest restriction on a 300 six. The C-Series manifold is designed to bridge the gap between stock and full competition setups, with strong mid-range and upper-rpm torque across a power band from about 2,500 to over 7,000 rpm. Offenhauser rates this manifold at up to 70 additional horsepower on an otherwise stock 240/300.

Carburetor fitment: It accepts standard square bore Holley or Carter 4-barrel carbs, with 500 CFM and larger recommended. Carbs clear the manifold without modification. An Offy universal linkage kit is recommended for most installs.

Our recommended setup: Add the Offenhauser 6227T Turtle Flow insert, then top it with an Edelbrock AVS2 650 CFM carburetor. Or upgrade to fuel injection with an Aces EFI Killshot 2 Pro or Aces Royal Flush 2 Pro throttle body system. We offer Aces EFI tuning, remote or in-shop.

Fitment: Fits all 1965–1996 Ford 240 and 300 inline six engines.

Specs: C-Series, natural aluminum finish, square bore flange. The rear openings are 3/8" and 1/4" NPT. Emissions provisions can be blocked off for competition use.

Availability: This is one of the most popular 300 six intakes, and it sells out fast. If it's on backorder, current lead time is about 8–10 weeks.