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).
On leaky gap performance, detailing engine speeds for different ignition timing settings.
| Identifier | ExFiles\Box 40\2\ Scan097 | |
| Date | 29th March 1926 guessed | |
| Leaky gap performance. - Will not spark at all in advance position Speeds :- 15° retarded 850 to 2200 rpm Central 500 to 2800 " Retard 230 to 4500 " | ||