650-850 CFM Secondary Metering Block

The Advanced Engine Design 650–850 CFM Secondary Metering Block is a precision aluminum component engineered for Holley 4150 carburetors seeking optimized fuel delivery control across the mid-to-high CFM range. This secondary metering block regulates fuel flow to the carburetor's secondary circuit, enabling smooth transition from primary to secondary jetting as engine demand increases. The chromate finish provides corrosion resistance, critical for longevity in high-heat engine bay environments and variable humidity storage conditions.

The 650–850 CFM capacity range makes this secondary metering block suitable for medium-displacement street engines and mild-to-moderate performance builds where progressive jetting is essential for drivability and fuel economy during cruise. The metering block's aluminum construction balances thermal conductivity—allowing consistent fuel temperature regulation—with lightweight construction that doesn't add unnecessary mass to carburetor assemblies. Proper secondary metering prevents lean-condition stumbles on acceleration and reduces carburetor surge, directly improving throttle response and engine stability across a wide RPM band.

Carburetor tuning specialists, hot rod builders, and street performance enthusiasts restoration work on vintage Holley 4150 platforms will find this OEM-style secondary metering block essential for baseline jetting setup or component replacement after cleaning and rebuild cycles. Holley 4150 carburetors remain popular in classic muscle car restorations, street rods, and budget-conscious racing applications where secondary metering accuracy directly affects part-throttle drivability and high-load performance.

Each metering block arrives ready for installation or tuning customization. Aluminum construction and chromate coating ensure dimensional stability and resistance to fuel and environmental exposure. Verify your carburetor CFM rating and secondary circuit configuration before ordering, as metering block sizing is application-specific.