Speedmaster 1-147-023 BBC 454 Hi-Rise Rectangular Port Intake Manifold Polished

The Speedmaster 1-147-023 is a high-performance single plane intake manifold engineered for Big Block Chevy 454 engines with rectangular port cylinder heads. This cast aluminum hi-rise manifold features an open plenum design optimized for high-RPM power delivery, with peak performance beginning around 3,000 rpm and continuing through the upper rev range.

Key Features:

• Cast aluminum construction with machine polished finish for show-quality appearance
• Single plane, open plenum design for maximum high-RPM airflow
• Accepts square-bore 4150-style carburetors (800 cfm or larger recommended)
• Rectangular port configuration: 1.69" wide x 2.31" tall at gasket flange
• Optimized runner design for 468-540 cubic inch displacement engines
• Nitrous oxide injection bosses for power adder compatibility
• Dual distributor hold-downs for secure installation
• Four corner water ports for proper coolant circulation
• Pressure tested to ensure leak-free performance

Installation Notes:

• Designed for rectangular port BBC cylinder heads only (not compatible with oval port heads)
• Port size can be enlarged to match gaskets or ported cylinder heads
• Use Fel-Pro intake gaskets #1211 (Printoseal) or #1275 (non-Printoseal) standard 1/16" thickness
• Fel-Pro #1239 (1/8" thick non-Printoseal) may be required if heads have been milled

This manifold is ideal for serious performance applications including street/strip racing, drag racing, and engine builds focused on top-end power. The hi-rise design positions the carburetor higher for improved air distribution and maximizes the potential of aggressive camshafts and high-compression combinations.