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).
Comparing valve diameters in Graham type cylinder heads versus the standard 25/30 unit.
| Identifier | ExFiles\Box 103\4\ scan0176 | |
| Date | 12th August 1936 | |
| x579 RHC.{R. H. Coverley - Production Engineer} From Hs{Lord Ernest Hives - Chair}/Swdl.{Len H. Swindell} Hs{Lord Ernest Hives - Chair}/Swdl.{Len H. Swindell}13/MA.12.8.36. 25/30. The Graham type of cylinder head Ex.22272 which is being fitted to B9 has we find been produced for valves which at the time of instruction were larger in diameter than at present used on the standard 25/30 unit. As the chief object of the Graham head is slow running will you please follow up with a head in which the casting is modified to take the present size of standard valves. Exhaust. Inlet. Throat diameter of Ex.22272 Valves. 1.3" 1.5" Throat diameter of standard valves. 1.225" 1.4" Hs{Lord Ernest Hives - Chair}/Swdl.{Len H. Swindell} | ||