CONSIDERATIONS FOR COMMERCIAL VALVE MAINTENANCE 530210
THE first step toward longer valve life as described in this paper, is a careful disassembly and inspection of the engine. Good judgment and care should then be used in correcting or replacing those parts that are scaled or damaged through previous usage.
When the engine is disassembled and inspected after a run, it may be found that some of the worn parts are still within wear limits that can be tolerated. The valve stem tip will show the first sign of tappet-screw or rocker-arm wear, which, if serious, will lead to erroneous tappet clearance readings. Regrinding may accomplish the correction. Extremely worn bushings or scuffed tappets should be replaced.
Valve guide wear should be carefully checked because it affects the overall valve temperature, the increase in clearance leading to less heat conductivity. The next consideration is the valve spring, for which the authors suggest the checking of five wear points.
It is pointed out that extreme care in the reconditioning of valve gear can be rendered useless by careless lash setting. Insufficient lash drastically reduces valve life, whereas excessive valve lash generally leads to broken valves.
The authors describe an effective means of rotation now available which does not require continuous maintenance to ensure its proper functioning.