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).
Cylinder head issues including valve seat distortion, valve spring problems, and an inefficient water pump.
| Identifier | ExFiles\Box 5a\3\ 03-page137 | |
| Date | 29th November 1931 | |
| 85840 To Hs{Lord Ernest Hives - Chair}/Rs.{Sir Henry Royce's Secretary} From S.W.H. Hotel de France, Chateauroux, FRANCE. 29/11/31. 18.G.IV. We have dismantled the cylinder head to ascertain the cause of lost exhaust valve clearance. The cause seems to be due to the valve seat distortion. We are again getting lopsided as was the case with 19.G.IV. The valve seats do not show the burning effect as on 19.G.IV. but the valves show bad pitting where the exhaust gas has been passing, (they evidently have not been rotating). The lop-sided bedding of the valves is caused by the coring for the valve port under the seating. This side of the seating has not got the same amount of metal and is collapsing (not a great amount) in exactly the same manner as did the cylinders before they were strutted. I am enclosing a sketch to try and show clearly what is taking place. We have also noted that all the valve crumpets have become compressed to their limit and the valve spring washers are resting on the metal. The bottom spring washers show that the valve springs have been fidgeting and have worn grooves in the washer face. In the alteration to the design of the valve guide for the high lift camshaft a feature has been omitted, that is, there should have been a groove turned round the top of the guide to coincide with the air hole drilled in the bottom spring washer to prevent capillary attraction of the oil down the valve stems. The condition of the Inlet Valves show that a lot of oil has been drawn down the guides, the valves being very wet when taken out. The top of the exhaust valve stems were carboned up making them very sluggish in closing, in fact when the valves were turned round, they would not go down on their seats. The temperature rise of the water during slow running is not caused by blockage in the cylinder head or cylinder passages. We believe that the cause is an inefficient water pump at slow speeds. G W Hancock G.{Mr Griffiths - Chief Accountant / Mr Gnapp} W. H.{Arthur M. Hanbury - Head Complaints} | ||