Carburetor - 670CFM Ultra Street Avenger

The Holley Carburetor - 670 CFM Ultra Street Avenger Model 4150 is a 4-barrel square-bore carburetor engineered for street and light performance applications requiring precise fuel metering and reliable cold-start capability. With 670 cubic feet per minute (CFM) flow capacity, this unit delivers the air-fuel mixture volume necessary for mid-range displacement engines while maintaining the vacuum secondary and electric choke design that prioritizes drivability over all-out peak power.

The 670 CFM specification reflects a balance point in carburetor selection: sufficient flow to support responsive acceleration without sacrificing idle quality or fuel economy on highway cruising. The vacuum secondary design meters fuel based on intake manifold depression rather than throttle position alone, reducing over-enrichment during partial-load operation. The electric choke provides consistent cold-start enrichment independent of ambient temperature or engine coolant lag. Dual inlet ports accommodate flexible fuel supply plumbing. Black anodized aluminum construction resists corrosion while the tumble-polished finish maintains appearance across climate conditions.

This carburetor is suited for street-driven vehicles where reliability and everyday usability take priority over racing performance. Owners performing engine rebuilds, carburetor restorations, or swaps on small-block to mid-sized engines benefit from the Ultra Street Avenger's reputation for consistent fuel delivery and reduced tuning sensitivity. The 4-barrel, square-bore configuration ensures compatibility with OEM and aftermarket intake manifolds designed for standard bolt patterns.

Carburetor selection depends on matching CFM capacity to engine displacement and intended duty cycle. The 670 CFM specification targets engines in the 300–400 cubic-inch range at street RPM. Oversizing creates bog and hesitation; undersizing limits top-end power. Holley's Ultra Street Avenger line balances these priorities for builders prioritizing driveability.