Double Pumper Billet Block Conversion Kit

The PROFORM Double Pumper Billet Block Conversion Kit transforms your Holley 4150 carburetor into a high-performance fuel delivery system designed for serious engine builders and hot rodders. This metering block assembly converts single-stage carburetors into true dual-stage units, enabling independent primary and secondary fuel circuits that respond dynamically to engine load and throttle input. Built for racers and enthusiasts who demand precise fuel mixture control across the RPM band, this conversion kit eliminates the limitations of single-pump designs and unlocks measurable gains in throttle response and mid-range power.

Machined from billet aluminum and finished in durable black anodize, the Double Pumper Billet Block Conversion Kit features precision-ported passages that optimize fuel atomization and distribution. The dual-pump design isolates primary (cruise and part-throttle) circuits from secondary (wide-open throttle) circuits, allowing each stage to meter fuel independently based on engine demand. This separation prevents the fuel-starvation issues common in single-pumper configurations and delivers consistent carburetion under hard acceleration, sustained load, and variable throttle conditions. The kit includes all necessary gaskets for a complete installation, ensuring proper sealing and eliminating leak points that compromise performance and reliability.

This conversion kit is ideal for street machines, bracket racers, and engine builders retrofitting older or replacement Holley 4150 carburetors seeking improved fuel delivery architecture. Installation requires basic carburetor disassembly and familiarity with metering block replacement procedures; most experienced mechanics complete the conversion in under two hours. The compact 4.35" × 2.4" × 6.75" footprint maintains factory carburetor mounting geometry, ensuring bolt-on compatibility with existing intake manifolds and linkage. Owners of classic muscle cars, drag cars, and street rods benefit most from this upgrade, as the independent pump circuits provide the precise fuel control necessary for repeatability in high-load situations where carburetor tuning directly impacts performance and drivability.