A combustion engine component comprises an assembly of a belt pulley for driving auxiliary engine equipment and a torsional vibration damper. The assembly is adapted to be fixed on an engine crankshaft, wherein the belt pulley is of a so called decoupling type, arranged to be able to change its rotational angle relative to the crankshaft and the torsional vibration damper. The torsional vibration damper is partially positioned in a corresponding annular recess in the belt pulley, creating an annular cavity in the recess between the torsional vibration damper and the belt pulley. An annular seal ring is positioned in the annular cavity and is arranged to close off at least a part of the annular cavity from the air surrounding the assembly.