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).
Valve types, tappet clearances, valve springs, and suspension components for various models.
| Identifier | ExFiles\Box 101\1\ scan0225 | |
| Date | 24th April 1936 | |
| -2- Hs{Lord Ernest Hives - Chair}/Rm.{William Robotham - Chief Engineer}28/KW.24.4.36. In view of this fact we have put two types of valve in 22-G-V, one is exactly the same as the Bentley only with reduced diameter, and the other is the tulip valve which has recently been designed. We want to watch these valves closely for stretch. Another point is, we want recommendations for the tappet clearances we can use for ordinary touring conditions in England without all the clearance being taken up. On the Bentley we recommend .004" exhaust and inlet for English conditions, increasing to .006" exhaust for Continental work. It is possible that if the 20/25 gets hotter, these clearance recommendations will be insufficient. The other point is the valve springs. We did not fit Bentley valve springs to this head originally because we were afraid of running into the crankshaft master period. Also we do not want to fit stronger valve springs than are necessary because of (1) increase in tendency to engine gear rattles, and (2) increase in tappet noise. We have sent the car over with the valve springs which were fitted before. We should like to know the valve bouncing speed of these springs, and then will you change the springs over and fit the Bentley springs, telling us whether you notice any increase in timing gear rattle and tappet noise generally, and also whether it enables you to drive on to the crankshaft period. With regard to the Phantom III, we have been having tremendous arguments concerning rubber shackles and the like, and we have now agreed to send the car out without rubber shackles but with provision made for incorporating them during the test. The top spring leaf has been the big job and we shall not get any for another fortnight. We shall send the car out with standard springs and we hope to get it away towards the end of next week. I may bring it out myself, as you will be fully occupied. | ||