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).
Comparison of specifications for the 40/50 and 20/25 models, including capacity, downtake, and swanneck dimensions, along with their ratios.
| Identifier | ExFiles\Box 6\7\ 07-page115 | |
| Date | 6th May 1931 | |
| FOR FILES. YS-30 6.5.31. X.7230. X.5230. Capacity. Downtake. Swanneck. 40/50. 7668 cc's. 3.0" Dia. 2.0" Dia. 7.06 sq.in. 3.14 sq.in. 20/25. 3670 cc's. 2.0" 1.5" 3.14. 1.76. Ratio .48 .442 .56 By/SS.{S. Smith} | ||