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).
Potential engine improvements related to spark plug position, valve port efficiency, and cylinder head design.
| Identifier | ExFiles\Box 124\2\ scan0395 | |
| Date | 5th February 1944 | |
| - 2 - 3. SPARK PLUG POSITION. The high-power head is highly critical to spark plug position and I think we may waste time if we start moving this about in order to improve the inlet port. 4. ORIFICE CO-EFFICIENT VALVE AND PORT. When we come to improving the orifice co-efficient of valve and port, if we are successful - we get something for nothing. Under idling conditions, the gas flow is so small that the shape of valve and port can hardly make any difference. At high speeds, however, a 5% increase in power would be most attractive. I do not think that we shall have to alter the port bend appreciably because if we take our naturally aspirated Merlin engine, which gives over 131 B.M.E.P. effective pressure at 6-1 compression ratio, with the carburetter in the V, the mixture goes through more than 360º in bends. The Kestrel, as I remember it, gave even better results. Some work has been done at Derby improving the valve and port on the Merlin, and I should like to have a summary of this. 5. MYTH ALTERNATIVE CYLINDER HEAD. This has two entirely different shapes of inlet valve port, and 2 spark plug positions and should give us a mass of information in a very short time. 6. EXHAUST VALVE SIZES. Here again, unless I am very mistaken, we tried two different exhaust valve sizes in the early days of the high power head, and got no advantage out of the bigger valve. This should be confirmed by extracts from Swindell's Reports. Summarising the position, an immense amount of information is available in our files. Someone should make a precis of this and it should be available for a general discussion before we do anything other than tackle the valve shape and the shape of the seat and port immediately adjacent to the valve head. Rm.{William Robotham - Chief Engineer} | ||