1999 Volvo Penta "WT" Models Workshop Manual, Page 133Get this manual
INote Clean: All parts in clean solvent and dry them with compressed air Make sure oil passages in valve push rods are clearInspect: Valve rocker arms and balls at their mating surfacesThese surfaces should be free from wear or any damage Valve rocker arm areas that contact the valve stems and the socket areas that contact the ends of the valve push rodsThese areas should be free of damage or wear Valve rocker arm nuts Valve push rod ends for scoring, roughness, or bendsINotel Roll the valve push rod on flat surface to determine its straightnessIf the rod is bent, the rod will not roll freelyReplace if necessary
Valve Lifters
This engine uses hydraulic valve liftersValve lifters are serviced only as an assemblyNo internal parts are availableService is limited to disassembly and cleaningDiscard valve lifters that are excessively worn or damagedWhenever the camshaft needs to be replaced, new set of valve lifters must also be installed