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).
List of proposed engine modifications regarding valve springs, camshaft, push rods, and tappets.
| Identifier | ExFiles\Box 17\6\ Scan309 | |
| Date | 6th September 1934 | |
| -2- Hs{Lord Ernest Hives - Chair}/Rn.{Mr Robinson}11/KW. 6.9.34. (3) We anticipate that to maintain the same valve bouncing speed it will be necessary to increase the valve spring load in the ratio of 1.2 to 1. This is easily obtainable on the 20/25; on the Bentley we suggest an outer spring as near as possible to the present standard spring with the inner spring to EB.5084. (4) Central camshaft feed. (5) Valves lightened as on Hs.{Lord Ernest Hives - Chair}1450/1. (6) Duralumin push rods. (7) The head to be designed with a split rocker shaft as on the present aluminium Bentley head. This will enable us to use any material we may in the future find desirable. (8) The Cadillac silent tappet runs with a clearance equivalent to .001. At present on the Bentley we run with a clearance of .005 approximately. There is no doubt that the slow running suffers if we reduce the clearance to .001. For this reason we should like a camshaft with modifications to compensate for this. On the present Bentley camshaft advantage is not taken of the fact that a shorter toe can be used on the opening and on the closing for a given degree of silence. It may be necessary to slightly reduce the overlap, and we recommend that the inlet does not close later than at present. (9) While on the subject of valve gear, we think that the Bentley tappet should be brought into line with the Phantom and lightened. If we can do this as well as lighten the valves we may be able to retain the present standard valve springs. If we can improve the method of lubricating the tappet at the same time it would be an advantage. (10) 28-EX. We shall require an oil filter as on | ||