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).
List of four different engine unit types, specifying cylinder count and bore size.
| Identifier | ExFiles\Box 111\2\ scan0390 | |
| Date | 14th September 1938 | |
| -2- Rm{William Robotham - Chief Engineer}6/R.14.9.38. (1) 6-cyl. Cast Iron Unit 3¼" bore. (2) Straight 8 Cast Iron Unit 3¼" bore. (3) 6-cyl. Cast Iron Unit 3½" bore. (4) Straight 8 Reduced Weight Unit 3½" bore. Rm.{William Robotham - Chief Engineer} | ||