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).
Graph showing the ignition advance that causes audible detonation at constant speed and full load, comparing standard and long duration cams.
| Identifier | ExFiles\Box 66a\2\ scan0228 | |
| Date | 15th August 1919 guessed | |
| IGNITION ADVANCE WHICH JUST CAUSES AUDIBLE DETONATION AT A CONSTANT SPEED, FULL LOAD. IGNITION ADVANCE 60 50 40 30 20 10 500 600 700 800 900 1000 R.P.M. LONG DURATION CAMS STD. | ||