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).
The investigation and redesign of high power cylinder heads to improve performance.
| Identifier | ExFiles\Box 132\4\ scan0224 | |
| Date | 12th October 1939 | |
| 1124 + 1129 To Ev.{Ivan Evernden - coachwork} c. to Jnr.{Charles L. Jenner} c. to Rm{William Robotham - Chief Engineer}/Gry.{Shadwell Grylls} c. to Rm{William Robotham - Chief Engineer}/Wym.{G. Harold Whyman - Experimental Manager} c. to Rm{William Robotham - Chief Engineer}/OJS. Rm{William Robotham - Chief Engineer}/Swdl.{Len H. Swindell}2/JH.12.10.39. HIGH POWER CYLINDER HEADS. Further to our report Rm{William Robotham - Chief Engineer}/Swdl.{Len H. Swindell}2/MH.{M. Huckerby}1.2.39. regarding the investigation of the original high power head the conclusive points were as follows :- (1) Advantage of freedom from detonations was obtained by increasing the original throat area from 1.44 sq.in. to 1.64 sq.in (PD.292) the latter figure being the maximum area possible on this type of head without redesign. (2) Any attempt to increase the compression ratio above the original figure of 6.25 : 1 by machining off the face of the cylinder head, in effect, reducing the throat area increased the detonations such that no gain was obtained with the higher ratio. (3) The nearer the piston to the cylinder head the better the anti detonating characteristics. NOTE :- The original head EB.3844 is shown on the attached sketch S.90. In accordance with the above findings two alternative heads were produced as follows :- (1) EB.4706 complete redesign and new patterns etc. giving 7.0 : 1 compression ratio, the features of this head being - (a) Exceptionally large throat. (b) Clearance above the exhaust valve reduced. (c) Shorter and more compact combustion chamber by extending the "squish" portion over the piston. (d) Increased inclination of the inlet valve to facilitate the above. This head is also shown on attached sketch S.90. | ||