The Model 425 mixer is typically used on larger V8 engines in the range of 305 to 445 CID. Engines larger than 445 RPM would have lower maximum engine speeds.
Since the Model 425 mixer is 6.25" tall, it is normally used in dual fuel applications turned 90° sideways. Commonly used adapters for carburetors with 5-1/8" air horns are the AA2-40 (90º x 4¾" tall) and the low-profile AA2-46 Air Horn Adapter (90º x 3½" tall).
Using the Model 425 mixer in this orientation leads to premature wear on the gas valve. This mixer was designed for vertical use and the gas valve's orifice will tend to wear egg-shaped over time when used on its side.
This is dual fuel system using a Model 425 mixer and a AA2-40 adapter on a TBI engine. This type of system requires an propane system system controller to manage timing advance, fuel mixture control, and gasoline injector simulators. Without an integrated controller, the engine management system would generate check engine faults. A better alternative is to use an propane injection conversion with the propane injectors controlled by the vehicle's PCM.