BBC EFI O/P Intake Manifold w/4150 Flange

The Holley BBC EFI O/P Intake Manifold with 4150 Flange (Part No. 300-561) is a single-plane aluminum intake manifold engineered for big-block Chevy EFI applications requiring a square-bore, oval-port configuration. This is purpose-built fuel-injection hardware designed for builders targeting high-RPM performance and modern engine management integration without sacrificing the structural integrity and thermal characteristics of aluminum construction.

The single-plane design promotes velocity and scavenging efficiency across the RPM band, while the oval-port layout optimizes flow characteristics for big-block cylinder heads. The 4150 flange standardizes mounting compatibility with a wide range of EFI throttle bodies and carburetors, ensuring flexibility during build planning. At 23.2 lbs, the manifold presents a manageable weight penalty compared to cast-iron alternatives, while the natural aluminum finish allows for secondary coating or polishing to match engine bay aesthetics. Dimensions of 12.5 x 12.25 x 24.6 inches reflect the footprint typical of single-plane designs—builders should verify clearance with their specific engine bay configuration and accessory placement before ordering.

This manifold is suited for street and strip applications where modern EFI tuning is preferred over carburetor setups. Big-block Chevy builders undertaking a complete fuel-injection retrofit, or those upgrading from older induction systems to electronic fuel management, will find this Holley piece a direct bolt-on solution that maintains OEM reliability while preserving the performance envelope of modern engine control units. The 4150 flange standard ensures long-term parts availability and aftermarket support.