On engine modifications for Bentley model 4-B-IV, comparing compression ratios and noting horsepower increase.
| Identifier | ExFiles\Box 88\2\ scan0071 | |
| Date | 28th November 1934 | |
| To Sg. {Arthur F. Sidgreaves - MD} from Hs {Lord Ernest Hives - Chair} /Rm. {William Robotham - Chief Engineer} c. to Wor. {Arthur Wormald - General Works Manager} c. to E. {Mr Elliott - Chief Engineer} Hs {Lord Ernest Hives - Chair} /Rm. {William Robotham - Chief Engineer} 18/KN. {D. G. McKechnie - Sales} 28.11.34. 4-B-IV. Replying to Sg. {Arthur F. Sidgreaves - MD} 6/E.26.11.34. Standard Bentley - 6.4 compression ratio. The head on 4-B-IV is 6.9 compression ratio. In addition, it has slightly larger inlet valves. These two modifications give an increase of about 6 or 7 H.P. at 4,000 engine r.p.m. Hs {Lord Ernest Hives - Chair} /Rm. {William Robotham - Chief Engineer} | ||
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).