When can a reciprocating engine using hydraulic valve lifters expect to have no clearance in its valve-operating mechanism after reaching minimum inlet oil and cylinder head temperatures?

A reciprocating engine that uses hydraulic valve lifters is designed such that the clearance between the valve-operating mechanism components is minimized during normal operation once the engine reaches its specified operating temperatures. Hydraulic lifters are filled with oil to maintain proper clearance and ensure consistent operation of the valves.

As the engine operates and reaches the minimum inlet oil and cylinder head temperatures, the oil becomes less viscous, allowing the lifters to adjust and maintain a precise fit within the valve train. This action eliminates any undesired clearance that would otherwise lead to excessive wear or inefficiency in valve operation.

In contrast, if lifters become deflated, there will be increased clearance, leading to potential damage. Additionally, carbon and sludge buildup could interfere with the lifter's ability to operate correctly, potentially resulting in increased clearance rather than none at all. Lastly, during initial start-up, the engine components, including the hydraulic lifters, may not yet be primed with oil, resulting in some clearance until the system is fully lubricated. Thus, none of these situations align with the conditions of normal engine operation when clearance should be at a minimum.