The Holley GM LS1/LS2/LS6 Hi-Ram lower manifold is a modular alternative to fabricated sheet-metal intakes for naturally aspirated or forced-induction engines in the 6.0-7.0+ liter range, built for a 3,500-8,000 RPM power band.
Specifications:
- Engine: GM LS1/LS2/LS6
- Basic Operating RPM Range: 3,500-8,000
- Cylinder Head Port Shape: Cathedral
- Deck Height: 9.24"
- Fuel System Type: EFI
- Finish: Silver/Natural
- Construction: Cast Aluminum
- Type of Component: Lower Manifold
- Vacuum Ports: Yes
- Mounting Flange Gasket Type: Standard LS3 molded O-ring
- Port Size: 2.49" H x 1.21" W
- Plenum Top Gasket Type: 3/32" round O-ring cord
- Runner Length: 6.58" as-cast, tapered 4.25 to 2.53 in² cross-section
- Fuel Rails: -8AN O-ring fittings, come standard with EFI Hi-Ram kits
- Part Number: 300-227
Recommended for performance, racing, and street rod applications where hood restrictions aren't a consideration. Plenum top ordered separately.
Compliance: This part is legal for sale and use on Racing Use Only Vehicles — competition vehicles that are not registered and never operated on the street. It is against the law to install this part on an Emissions Controlled Vehicle (1966-and-newer California-certified or 1968-and-newer federally certified vehicles).
FAQ
What engines does the 300-227 fit?
GM LS1/LS2/LS6 engines with cathedral-port cylinder heads.
Does it include a plenum top?
No — this is the lower manifold base only; a plenum top is ordered separately.
What RPM range is it built for?
3,500-8,000 RPM, intended for engines in the 6.0 to 7.0+ liter range at 7,000-8,000+ RPM max power.
