On the Motorcraft 2150 (and the earlier 2100) carburetor, that lever located between the bores on the throttle shaft is the Mechanical Power Valve Actuator.|
While the primary power valve is vacuum-operated to provide extra fuel under load, this mechanical linkage serves as a "fail-safe" or supplemental enrichment system.
How It Functions
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WOT Enrichment: When you move the throttle to Wide Open Throttle (WOT), the throttle shaft rotates to a point where this lever physically pushes up on a pin or rod (often associated with the power valve or a separate enrichment circuit, depending on the specific year and calibration).
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Fuel Delivery: It ensures that even if engine vacuum is fluctuating or slightly too high to trigger the vacuum-operated power valve, the engine still receives the maximum required fuel for full-throttle acceleration.
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Preventing "Lean-Out": Its main job is to prevent the engine from running lean during high-demand situations, which protects the engine from detonation and overheating.
Key Maintenance Note
When rebuilding these units, ensure that this lever is not bent or binding. If it doesn't move freely with the throttle shaft, you might experience a "flat spot" or hesitation when you floor the accelerator.
