Blueprint graph of a 4 1/4 Litre Bentley engine showing B.HP and Ignition Advance vs R.P.M. for different compression ratios.
| Identifier | ExFiles\Box 148\1\ scan0036 | |
| Date | 1st January 1939 guessed | |
| 4 1/4 LITRE BENTLEY B.V. (COMP. RATIO) S. 63 (1) COMP. RATIO 6.6:1 .170 CROWN .030 GASKET (2) COMP. RATIO 7.0:1 .100 CROWN) .060 GASKET (3) COMP INCR. .030 CROWN ROAD MASTER ADV. TO AVOID DETN. MIN ADV. FOR MAX POWER A) = LOSS BY AVOIDING DETN. B.H.P R.P.M. IGN ADV DEGREES B.T.D.C. WRAITH CYL HEAD (30 C.S) N VALVE .180. 4 1/4 EXH SYSTEM EST STD EXH SYSTEM SHELL NO 1 PETROL AMSHAFT EN 21370. | ||
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).