The valve spindle K 27511 is the hardened, precision-turned stem that transmits motion between the rocker/actuator and the inlet valve head in the Sulzer ZV40/48. Its straightness, surface finish and dimensional tolerance are crucial: the spindle must run true in the valve guide, resist bending under side loads and present a wear-resistant surface for the guide and seal. Made from alloy steel and often surface-hardened or coated, K 27511 directly affects sealing performance and valve timing — scoring, bending or excessive wear on the spindle will degrade combustion efficiency and should trigger guide inspection and component replacement to restore reliable engine operation.