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).
Log page with diagrams and notes comparing spark plug conditions under different settings.
| Identifier | ExFiles\Box 63\4\ scan0009 | |
| Date | 26th May 1918 guessed | |
| (9) (31) ZR6/2000/5/R/A As above. (32) ZR6/2000/5/R/B Ditto (33) ZR6/2000/7/A/A as above. (34) ZR6/2000/7/A/B Ditto. (35) ZR6/2000/7/R/A as above. Spark takes place more easily at retard than at advance. (36) ZR6/2000/7/R/B Ditto. | ||