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).
Summary of the design history and issues with Phantom II exhaust valves.
| Identifier | ExFiles\Box 131\4\ scan0356 | |
| Date | 29th June 1937 | |
| E/MCS.1/HP.29.6.37. Phantom II Exhaust Valves - re Rm{William Robotham - Chief Engineer}/GWH.{George W. Hancock - Head Chateauroux}25.6.37. E.78493 - Standard prior to Series 02 (.4325 dia. stem). These valves gave trouble by cracking round head of valve. LeC.2551 was designed with stem dia. increased to .460, and head made tulip shape. These valves also cracked and stretched at tulip. Flat headed valves with .460 dia. stems were next tried and these also failed in the same place as previous valves, but were on production (E.83095) from 51st chassis in 02 Series to 122nd chassis in 02 Series only. The next design was to LeC.3303 which retained the .460 dia. stem with a strengthened semi-tulip shaped head (details E.83700 and E.85505). These were on production from 123rd chassis in 02 Series to the end of Phantom II production. When Phantom II was being tried with hydraulic tappets it was found necessary to lighten the exhaust valve to avoid valve bounce and this was done by LeC.3960 and detail E.85640, the stem being reduced to .4325 dia. and the semi-tulip head lightened. These valves were only run experimentally. When designing LeC.3960 it was decided that the larger diameter stem had not cured the valve breakages, as these continued until the semi tulip shaped head was used, and for this reason we reverted to the original stem diameter to save weight, but we do not know whether valves to LeC. 3960 had sufficient running to recommend them for replacement on standard cars. They are 1 oz. lighter than the standard valves. E/McSTAY. | ||