Ventilspiels

Ventilspiels is the term used in some German-speaking technical contexts to refer to valve clearance, the small deliberate gap between a valve and the corresponding actuation mechanism in an internal combustion engine. This clearance, also known as valve lash, allows for thermal expansion, wear, and the mechanical tolerances of camshafts, rocker arms, and lifters so that valves can open and close reliably.

The importance of Ventilspiels lies in proper valve seating and engine geometry. If the clearance is too small, the valve may not fully close, leading to burned valves, reduced compression, and overheating. If the clearance is too large, the valve may open later or not seal well, causing rough idling, reduced low-end torque, increased fuel consumption, and audible tapping or clattering noises.

Measurement and adjustment procedures vary by engine design. A typical method involves cooling or warming the engine to a specified temperature, removing covers to access the valve train, and using a feeler gauge to measure the gap between the cam follower or rocker arm and the valve stem (or between the cam lobe and lifter, depending on the layout). Adjustment is achieved by installing shims, turning adjustment screws, or replacing lifters or rocker components to reach the manufacturer's specification. After adjustment, the engine is reassembled and tested.

Modern engines often employ hydraulic lash adjusters that automatically compensate for minor changes in clearance, reducing maintenance needs. In contrast, engines with solid lifters generally require periodic inspection and manual adjustment according to service intervals.

Notes: Ventilspiels is the German term for valve clearance; singular is Ventilspiel and plural is Ventilspiele. The exact specification is engine- and manufacturer-specific.