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).
Table of average engine bore wear measurements for 3.5 and 4.25 litre chassis over the years 1935 to 1938.
| Identifier | ExFiles\Box 131\2\ scan0292 | |
| Date | 25th October 1938 guessed | |
| 1935. 1936. 1937. 1938. Average bore wear of 20 chassis at 20,000 miles. 3½ L. .0045" .0044" Average bore wear of 10 chassis at 20,000 miles. 3½ L. .0040" .0044" ditto at 30,000 3½ L. .0047" .0051" Average bore wear of 10 chassis at 20,000 miles. 4¼ L. .0063" .0050" ditto at 30,000 miles. 4¼ L. .0050" .0060" crown measurement. | ||