New 75 m/m cylinder head design, its compression ratio, and a potential valve clearance issue.
| Identifier | ExFiles\Box 132\4\ scan0259 | |
| Date | 7th July 1941 | |
| WYMAN (crossed out) Rather high? Rm {William Robotham - Chief Engineer} (circled) 1124 To Rm. {William Robotham - Chief Engineer} from Jnr. {Charles L. Jenner} c. to Rm {William Robotham - Chief Engineer} /HH. RM {William Robotham - Chief Engineer} TOO HIGH Jnr. {Charles L. Jenner} 2/SW.7.7.41. 6.4:1 is now on the limit with present day fuel Rm {William Robotham - Chief Engineer} /Wyman. 75 m {Mr Moon / Mr Moore} /m. Cylinder Head. We have made a design of the original type Cylinder Head to supercede the intermediate type. A compression ratio of 6.75 : 1 has been chosen as suitable for this size of engine. The form of the head is exactly the same as for the 3 1/4 bore, but shallower, it will be noticed that the inlet valve will foul the piston if it remains stuck open at full lift. We have to accept this with a rationalized cylinder block. Jnr. {Charles L. Jenner} (initials) Original of PL.753 to Rm {William Robotham - Chief Engineer} /HH. Prints to Ashby and Jnr. {Charles L. Jenner} | ||
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).