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).
To R.M/R.Child regarding the thread length of Champion Y4 spark plugs.
| Identifier | ExFiles\Box 162\3\ img164 | |
| Date | 30th January 1940 | |
| Misc General 6000 To RM{William Robotham - Chief Engineer}/R.CHILD CHAMPION Y4 SPARK PLUGS. Re your query of yesterday:- It was 21.3.39 when you gave me the model & the length of thread was 16 M/M.{Mr Moon / Mr Moore} At the time, You mentioned that the plug could be supplied with a length of 12 M/M.{Mr Moon / Mr Moore} The desirable length is 16 M/M.{Mr Moon / Mr Moore} JNR.{Charles L. Jenner} | ||