Twin 58mm Throttle Body - 89-92 305/350 TPI

The Twin 58mm Throttle Body for 89-92 305/350 TPI engines represents a direct upgrade path for GM small-block carbureted and fuel-injected platforms seeking improved throttle response and airflow consistency. Designed for serious engine builders and performance enthusiasts, this BBK Performance unit replaces restrictive OEM throttle bodies that limit mid-range horsepower and fuel atomization. The dual 58mm bore configuration is engineered to supply adequate air volume for naturally aspirated and light-boost applications without sacrificing drivability or low-end torque.

Constructed from cast aluminum and finished in natural (unpainted) form, the Twin 58mm Throttle Body features twin blade design with stock flange mounting compatibility, enabling bolt-in installation on 305 and 350 TPI platforms without custom fabrication. The twin-bore architecture distributes incoming air evenly across both cylinders, reducing turbulence and improving charge density under load. Aluminum construction provides superior thermal stability compared to cast iron, minimizing heat soak that typically degrades metering accuracy in high-performance driving conditions. The 58mm diameter provides optimal balance between velocity and volume—large enough to feed naturally aspirated engine demands while maintaining sufficient air speed for proper fuel film atomization in the intake runners.

This throttle body is ideal for 1989–1992 Chevrolet small-block TPI conversions, restorations using modern fuel-injection retrofits, and street/strip builds requiring increased induction efficiency. The stock flange design ensures straightforward installation without adapter plates or custom intake modifications, making it compatible with both original and aftermarket intake manifolds fitted with TPI mounting surfaces. Typical applications include carbureted-to-fuel-injection conversions, performance cam upgrades, and mild forced-induction setups where OEM air delivery becomes the limiting factor. Weight of 3.8 lbs keeps rotating mass minimal, supporting quicker throttle tip-in response across the entire RPM range.