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 power increase in a 20 HP engine due to using larger valves.
| Identifier | ExFiles\Box 19\7\ Scan107 | |
| Date | 31th March 1927 | |
| 20 H.P. POWER INCREASE DUE TO LARGER VALVES. ENGINE No 11-GII. COMPRESSION RATIO = 5.45 to 1 OPEN EXHAUST. TWO ZENITH TRIPLE VENTURI HORIZONTAL CARBURETTERS. CORRECTED TO N.T.P. 31-3-27 B.H.P LARGE VALVES. (1.400 DIA) STANDARD VALVES. (1.200 DIA) B.M.E.P LARGE VALVES (1.400 DIA) STANDARD VALVES (1.200 DIA) BRAKE HORSE POWER R.P.M. OF ENGINE. BRAKE MEAN EFFECTIVE PRESSURE (LBS/SQ") 2 | ||