From the Rolls-Royce experimental archive: a quarter of a million communications from Rolls-Royce, 1906 to 1960's. Documents from the Sir Henry Royce Memorial Foundation (SHRMF).
Investigation into engine valve knocking, detailing experiments with lubrication, clearance adjustments, and component replacement.
| Identifier | ExFiles\Box 66a\2\ scan0016 | |
| Date | 19th March 1926 guessed | |
| contd :- -3- square to take up a position and operate at a tangent to the valve stem, thereby wearing the valve guide unevenly also having a tendency to make the valve rock on its seating. The knock still being there we tried to damp it out by lubricating the valve stem and seat. This we were successful in doing, immediately the oil was squirted on to the valve guide (having removed the felt washer), the knocking ceased. This proved that in some way the knock was coming from the valve. We also found that by placing a .004" feeler gauge between the rocker pad and valve thus reducing the clearance to .004", we almost cured the knock. This led us to believe that we were not getting the advantage of the design of the foot of the cam, and that the valve velocity in closing was too great with .008" clearance. The design shows that the velocity of the valve is the same up to a clearance of .013". We do not however quite agree with this, and believe that in practice we do gain an advantage of the foot of the cam when the valve clearance is set to .004". We then dismantled the cylinder head and examined the valve seats. We found that the seats of the two noisy valves were not true to the valve guide, and when the valves were seating they clicked over into position. We also found that wear had taken place in the valve guides due to the action of the valves and thrust of the rocker arm. We fitted one new valve guide to one valve and replaced the other valve by a new one. In both cases we carefully recut the valve seats making sure that they were true with the valve guides. contd :- | ||