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).
Testing 'Hemiss' spark plug adaptors, concluding they offered no advantage.
| Identifier | ExFiles\Box 162\3\ img128 | |
| Date | 15th January 1932 | |
| It was therefore thought to be a good engine on which to test the 'Hemiss' adaptors, & they were accordingly fitted to such plugs. After running in use for a week no perceptible or definite improvement in the missing trouble could be detected. The adaptors were accordingly removed, & the misfiring when cold after standing overnight checked & it is confirmed that there was no difference whether the adaptors were fitted or not. When the hot engine was test there was a slight misfire at low speeds (idling) with the 'Hemiss' adaptors fitted - this was not present in the standard condition. Summary No appreciable advantage is obtained by the use of Hemiss spark plug adaptors - & if anything the reverse is true. | ||