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).
Suitable fuels and spark plug thread specifications for a Bentley head.
| Identifier | ExFiles\Box 88\1\ scan0216 | |
| Date | 28th November 1935 | |
| -2- He/Rm.{William Robotham - Chief Engineer}24/KW.28.11.35. We have not had any trouble with sticking valves, but then we do not have your temperature variation. If you can find a benzol mixture which will enable you to run without detonation, we recommend that you should run on it. Alcohol fuels, on the other hand, have certain undesirable characteristics so that we do not recommend them where other fuels can be obtained having the requisite knock rating. With regard to the sparking plug thread in the Bentley head, the full specification of this is as follows 14.125 m.m. full dia. 1.250 m.m. pitch. 60º thread angle. Yours faithfully, FOR ROLLS-ROYCE LIMITED. | ||