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 comparison graph for an Aluminium Phantom engine with different valve sizes.
| Identifier | ExFiles\Box 17\6\ Scan015 | |
| Date | 2nd December 1926 guessed | |
| SHEET 3. BRAKE HORSE POWER .B.M.E.P (LBS. PER SQ. IN.) R.P.M. OF ENGINE. LARGE VALVES. B.H.P. B.M.E.P. SMALL VALVES. B.H.P. B.M.E.P. ALUM. PHANTOM POWER COMPARISON FOR 1.600 DIA & 1.750 DIA VALVES. COMP: RATIO = 4.89 : 1 Corrected N.T.P. | ||