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).
Blueprint detailing a modification to a Phantom II cylinder head to raise the compression ratio.
| Identifier | ExFiles\Box 14\3\ Scan060 | |
| Date | 10th January 1931 | |
| RAISING COMPRESSION RATIO PHANTOM II HEAD. .125 ROLLS-ROYCE LIMITED 10 JAN 31 | ||