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).
Power output performance graph for a 20/25 HP engine with different cylinder head specifications.
| Identifier | ExFiles\Box 27a\1\ Scan199 | |
| Date | 17th February 1934 | |
| 20/25 HP POWER OUTPUT (CYLINDER HEAD) UNIT C10 SPEC: ① COMP. RATIO - 5.75:1 - K.L.G. K.1. PLUGS ② " " - 6.3:1 - " K.S.5 " " OTHERWISE STANDARD 20/25 HP ENGINE OPEN EXHAUST B.H.P. R.P.M B.M.E.P. CTS{C. Trot Salt - Carburation} T.D.C 3.6° 10° 43° 4.4.5° (TAPPETS .020) | ||