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).
Engine performance, detonation, and proposed cylinder head design improvements.
| Identifier | ExFiles\Box 124\2\ scan0178 | |
| Date | 20th May 1940 | |
| -3- Cont'd.{John DeLooze - Company Secretary} one over the throat and one over the exhaust valve. The throat plug was found to be the best because (1) Detonation was at a minimum and power at a maximum. (2) Ignition advance was practically identical to standard Bentley. The exhaust plug gave far too great an advance, 40° at 1,000 r.p.m. (3) Slow running with weak mixtures was better. Referring to our hot exhaust valve and switching off trouble, as I mentioned there was a brand new head designed to overcome these difficulties, but it was a disappointment, it incorporated these features which we thought would improve the head. If you care to refer to PD.368 you will see them enumerated on the drawing. As far as I can remember they are as follows :- (A) The inlet valve was brought closer to the exhaust valve so that the inlet charge would sweep over the exhaust valve to some extent. (B) A generous throat. (C) Short flame travel. (D) More squish. (E) Spark plug point nearer to the inlet valve. Jnr.{Charles L. Jenner} | ||