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).
Instructions for achieving a 5.7 to 1 compression ratio for the 20/25 China model by machining a piston.
| Identifier | ExFiles\Box 103\4\ scan0083 | |
| Date | 2nd September 1931 | |
| Hs.{Lord Ernest Hives - Chair} RHO. X5050. BY/SS{S. Smith}6/N.2.9.31. 20/25 China. 5.7 to 1 Compression Ratio. To obtain 5.7 to 1 compression ratio using the production cylinder head, the top of the piston should be .031 below the upper face of the cylinder block. We suggest this could be done by machining .031 from the top of Piston E.56610. This piston is used in conjunction with Connecting Rod E.55608/9 (7.950 centres) for 2.000 dia. Crankpins. If the above piston is not available, any Turbulent Head combination of piston and conn. rod could be used. BY/SS.{S. Smith} | ||