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).
Report discussing engine detonation, alternative head designs, and a comparative table of valve gear specifications.
| Identifier | ExFiles\Box 113\5\ scan0210 | |
| Date | 13th February 1939 guessed | |
| -2- experienced on our cast-iron heads, that the noise is not so metallic. Curves taken on the bed however, shown in Fig. S8, seem to show that the detonation persists up to 1850 RPM as compared with 1000RPM on the standard Bentley 11 engine. This indication of poorer detonation qualities was borne out on the road, but it must be noted in connection with this, that very little work was done, and no real attempt made to obtain a good ignition governor. An alternative head was designed, which put the plug on the exhaust side instead of the inlet, and fired towards the inlet valves. The modification, it was anticipated, would materially improve the detonation properties, by putting the last gas to burn over the relatively cool inlet valves. No work however, other than design, was everdone on this head. Valve Gear- Considerable trouble was experienced with the valve gear and drive due partly to the exceptionally high ratio of lift to valve diameter figures as shown below, and partly due to oscillations to the chain drive. Valves. Throat Dia: Lift. % lift of diam: Duration over heavy accns. B 111 Inlet. 1.500 0.400 26.6% 242° Exhaust. 1.300 0.400 30.7% 247° B 60 Inlet. 1.750 0.400 22.9% 216° Exhaust. 1.500 0.375 25% 236° O.H.C. Inlet. 1.300 0.466 36.0% 232° Exhaust. 1.575 0.525 33.0% 244° Proposed Inlet. 1.300 0.350 27.0% - O.H.C. Exhaust. 1.575 0.450 28.5% - In view of the high lifts, and relatively long durations, the silencing toe on the cams was comparatively short, giving rise to noisy tappet operation, especially noticeable on the road. | ||