LS1 Cathedral Port Carburettor Street Single Plane EFI Int Manifold

Overview

Upgrade your GM LS performance with this Street Low Rise Cathedral Port EFI Intake Manifold. Crafted in a natural cast finish, this single-plane 4150 square-bore intake is engineered for LS1/LS2 cathedral-port heads in EFI configurations, delivering a steady, even air-fuel distribution for enhanced street and strip performance. Designed to sit atop your engine with a 4150 throttle body, it targets high-RPM efficiency and responsive throttle response.

Key Features

• EFI-specific single-plane intake manifold for GM LS Gen III/IV cathedral-port engines
• Natural cast finish; 4150 square-bore carburetor pad
• Low-rise design with an overall height of 122 mm (carb pad to bottom) – check bonnet clearance
• Port size: 0.95" x 2.45"; RPM operating range 2500 to 7000
• Carburettor studs: 5/16-18" (x4); 3/8" NPT port (x1); mounting holes: 6×5/16-18"
• Gasket O-Ring: AF6233-5002; intake manifold O-Rings included
• Compatibility: fits GM LS1/LS2 cathedral-port engines with EFI; not compatible with factory OEM fuel rails

What’s Included

• 8 × Intake Manifold O-Ring Gaskets (AF6233-5002)
• 4 × M6 × 1.00mm Hex Screws (80 mm UHL)
• 6 × M6 × 1.00mm Hex Screws (50 mm UHL)
• 10 × M6 Flat Washers
• 1 × 3/8" NPT Steel Port Plug

Fuel Rail Kit & EFI Accessories

• EFI applications require Aeroflow Fuel Rail Kit AF6999-5000 (included with this manifold)
• 2 × Fuel Rails (-8ORB)
• 1 × -8AN cross over braided line with two 90-degree non full-flow fittings
• 3 × -8AN to -8ORB fittings
• 1 × -8ORB hex port plug
• 6 × long mounting brackets; 6 × short mounting brackets
• 6 × 5/16-18" hex screws (18.5 mm UHL); 6 × 5/16-18" hex screws (12 mm UHL)
• 4 × M6 nuts
• 8 × 14 mm Injector O-Rings

Specifications & Compatibility

• Carburettor pad: 4150 flange
• Overall height (carb pad to bottom): 122 mm
• Port Size: 0.95" x 2.45"
• Intake gasket O-Ring: AF6233-5002
• Notes: For NON-EFI applications, use AF6040-5000
• Designed to convert GM LS engines to accept a 4150-style throttle body for retrofit applications
• Single-plane configuration optimized for steady air/fuel distribution at high RPM

Applications & Fitment

Specifically designed to suit GM LS Gen III and IV engines equipped with OE or aftermarket LS1/LS2 cathedral-port cylinder heads. The carburettor-mounting pad accepts aftermarket 4150 square-bore throttle bodies or adapter plates for turbocharged setups. This manifold is ideal for enthusiasts seeking a reliable EFI upgrade that preserves street drivability while enabling high-RPM performance.

Installation Notes

• EFI fuel rails are required; factory OEM rails are not compatible with this manifold
• Injector sizing: use 14 mm short (33.60 mm) injectors or 3/4" length (48.65 mm) injectors (sold separately)
• Check bonnet clearance due to the manifold height