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).
Performance graph comparing a standard 4¼ Litre Bentley engine with an O.H.C. conversion and altered timings.
| Identifier | ExFiles\Box 113\5\ scan0173 | |
| Date | 17th October 1936 | |
| 4¼ LITRE BENTLEY O.H.C. S.O. (CONVERTED UNIT) UNIT N° B.23. (1) STD 4¼ LITRE ENGINE (6.5:1 C/R) (2) O.H.C. CONVERSION (6.0:1 C.R.) (SPEC: RHC{R. H. Coverley - Production Engineer}/WSC.{W. S. Cassel}1/LS. 17.10.36) TIMING { I.O. 6° B.T. E.O. 43° B.B. , I.C. 29° A.B. E.C. 6° A.T. } (3) AS (2) BUT TIMING ALTERED:- { I.O. 2° A.T. E.O. 34° B.B. , I.C. 39° A.B. E.C. 11° A.T. } B.M.E.P. B.H.P. R.P.M. C.T.S. | ||