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).
Cylinder head capacity of a 3.5' bore Bentley engine and modifications needed for use on a 20/25 model.
| Identifier | ExFiles\Box 86\1\ scan0163 | |
| Date | 25th April 1935 | |
| x19 To RHC.{R. H. Coverley - Production Engineer} Hs{Lord Ernest Hives - Chair}/Rn.{Mr Robinson}12/KW. 25.4.35. 3 1/2" Bore Unit - Bentley. --------------------------- We understand that the capacity of the head prepared for the 3 1/2" bore engine on the Bentley is 109 c.c's. This gives a compression ratio of 6.80 to 1. Whilst this is alright for the Bentley it is too high for anything that can be fitted on the 20/25, and we should like sufficient metal to be left on the bottom face of the head which is being put through with the studs moved out, to give a cylinder head capacity of 120 c.c's. When the larger valves are fitted the trepanning necessary will doubtless increase the capacity appreciably. Hs{Lord Ernest Hives - Chair}/Rn.{Mr Robinson} | ||