Carburetor - 770CFM Ultra Street Avenger

The Carburetor - 770CFM Ultra Street Avenger (Model 4150) is a professional-grade four-barrel carburetor engineered for high-performance street and competition applications. Built by Holley, a manufacturer with decades of proven reliability in motorsports and demanding automotive environments, this 770 cubic feet per minute (CFM) unit delivers the precise fuel metering required for responsive throttle control and consistent performance across variable load conditions. Whether for drag racing, street performance builds, or serious engine tuning projects, the Ultra Street Avenger addresses the need for a carburetor that balances raw power delivery with streetable drivability.

This model features a square bore design with dual inlet ports, enabling optimized airflow distribution to each cylinder bank for even combustion and reduced lean-out conditions during hard acceleration. The electric choke provides automated cold-start enrichment without manual adjustment, while the vacuum secondary system automatically increases fuel flow as engine load increases—eliminating the hesitation common in older carburetors during off-idle transition. Construction from aluminum with black anodized and tumble-polished finishing resists corrosion and presents a professional appearance in engine bays. The 770 CFM rating strikes the practical sweet spot for small-block and mid-displacement engines, avoiding the oversizing that can cause bog and stumble during low-RPM cruising.

Experienced engine builders, performance technicians, and weekend racers will recognize the Ultra Street Avenger as a foundational choice for carbureted applications ranging from 350–500 cubic inch engines. Installation requires compatibility with square-bore intake manifolds and standard fuel delivery systems; proper jetting and float level adjustment during initial setup are essential for optimal tuning. At 10.2 pounds and compact footprint dimensions (11.2 x 7.9 x 12.4 inches), it fits most traditional engine bays without modification. This carburetor is backed by Holley's reputation for supporting enthusiasts with technical documentation, tuning guides, and replacement components for long-term reliability and customization.