When comparing the operating temperature valve clearance to cold valve clearance in a radial engine, what is the difference?

In a radial engine, as the engine operates, various components, including the valves, expand due to the increased temperature from combustion and friction. The operating temperature valve clearance is the space between the valve and the rocker arm when the engine is at normal operating temperature.

Due to thermal expansion, the materials of the components expand, leading to decreased clearance at higher temps. Cold valve clearance, measured when the engine is not running and at ambient temperature, indicates a larger gap, as the components are contracted.

Therefore, when comparing the two, the operating temperature valve clearance will be greater than the cold valve clearance because of this thermal expansion during operation. This factor is essential for ensuring proper valve operation and avoiding issues like valve damage or decreased engine performance.