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).
Issues with silichrome exhaust valves on 20/25 HP models due to leaded fuels, recommending a change to KE-965 valves.
| Identifier | ExFiles\Box 106\5\ scan0145 | |
| Date | 17th September 1935 | |
| X554 To Wor.{Arthur Wormald - General Works Manager} from Hs{Lord Ernest Hives - Chair}/Rm.{William Robotham - Chief Engineer} c. to E.{Mr Elliott - Chief Engineer} c. to By.{R.W. Bailey - Chief Engineer} Hs{Lord Ernest Hives - Chair}/Rm.{William Robotham - Chief Engineer}16/KW.17.9.35. 20/25 HP. Exhaust Valves. All Bentleys are now fitted with KE-965 exhaust valves. The change was made because it was found that the silichrome valves originally fitted would not withstand the attack of leaded fuels. The Bentley is of course a design to run on leaded fuels. The 20/25 exhaust valves were not changed at the same time as the Bentley because it is not necessary for this car to run on Esso; furthermore, we were not certain how KE-965 would behave with the 20/25 camshaft. The position has now arisen where the distribution of leaded fuels is so general that it is being used extensively on all cars. This year for the first time it is being used in France. Realising this, we used 21-G-IV to test out KE-965 valves against silichrome. At 7,800 miles one of the silichrome valves failed, the head came off and did a considerable amount of damage. The KE-965 valves were in much better condition. It is of course the high speed running which can be indulged in in France, combined with the leaded fuel, which caused the failure. It is certain, however, that now lead has been adopted over there this trouble is likely to happen on cars which are habitually running in France, and in course of time the valves will also deteriorate on 20/25's running in England. The KE-965 valves on 21-G-IV have now completed 10,000 miles and of course many such tests on the Bentley. We recommend that production should change to KE-965 with the least possible delay. The silichrome material could probably to a large extent be utilised for making inlet valves. Hs{Lord Ernest Hives - Chair}/Rm.{William Robotham - Chief Engineer} | ||