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).
Tabulated list comparing valve opening specifications for various engine models.
| Identifier | Morton\M19\ img215 | |
| Date | 8th August 1931 guessed | |
| TABULATED LIST OF VALVE OPENINGS. | Engine | Dia. of inlet valve. | Lift of inlet valve | Ratio Lift/Valve Dia. | Valve area per litre disp. | |---|---|---|---|---| | F.{Mr Friese} engine | 1.625 | .550 | .337 | 2.20 | | R.{Sir Henry Royce} engine | 1.950 | .570 | .292 | 1.84 | | 25 HP. .050 increased lift | 1.35 | .394 | .292 | 2.22 | | 25 HP. Standard. | 1.35 | .344 | .255 | 2.22 | | 40/50 New Camshaft L.A.C. 291B | 1.9 | .470 | .246 | 2.106 | | 40/50 Std. camshaft | 1.9 | .430 | .226 | 2.106 | | ||