Graph of power development for a 4¼ Litre Bentley engine, comparing performance at different compression ratios.
| Identifier | ExFiles\Box 90a\1\ Scan005 | |
| Date | 21th July 1938 guessed | |
| 4¼ LITRE BENTLEY POWER DEVELOPMENT B3 UNIT S.2 COMPRESSION-RATIO CYL HEAD Ex 22594 (IN. PORTS 1.625) CAMSHAFT EB 1085 C. 1 7/8 SU CARBS. ON 1 7/8 PIPE ① COMP RATIO 8.5:1 ② 9.0:1 ③ COMP RATIO 6.5:1 (N PORTS 1.850) STD CYL HEAD MON TO LEC S002 (DETURBULATED) STD N.D.N. SYSTEM I.O. 3° BT {Capt. J. S. Burt - Engineer} E.O. 47° BB I.C. 57° AB E.C. 6° AT TAPPETS .020 B.H.P. B.M.E.P. R.P.M. | ||
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).