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).
Exhaust valve pre-ignition issues and recommendations for valve shape and material.
| Identifier | ExFiles\Box 35\3\ scan 045 | |
| Date | 15th August 1923 | |
| R.R. 493A (40 M) (SL 42 15-7-23). J.H.,D.{John DeLooze - Company Secretary} EXPERIMENTAL REPORT. Expl. No. 2764 REF: He1/LC15.8.23. During our tests we proved that exhaust valves could be badly scaled, burnt and overheated by pre-ignition. In the case of the pre-ignition overheating it was generally over the whole diameter of the valve and not so locally as those which have failed in service. Tests show that the plugs over the valve pockets most readily pre-ignited. In many cases the same faulty plug in the centre position would seldom give trouble. We could obtain pre-ignition whether on coil or magneto & also whether we use pure benzol, Aviation or Grade 3 petrol. We recommend that as soon as possible we revert to the 45º angle seat and pre-war shape but still retain the 'Quickstep' material. We have carried out some preliminary tests with the latest mushroom shape valves. The results, although encouraging, do not show up to be any better than the pre-war shape, therefore, as we have had experience with thousands of these valves, we recommend that we return to that shape whilst we are proving the mushroom shape valve. If there is a question of using up a stock of valves, it would be permissible to use the present valves on the inlet; in that position they are entirely satisfactory. We suggest, however, that if we do that, we might have the angle of the valve seats all 45º so that it would not be very serious if they were changed about. We think this would be an advantage in repairs and replacements. It would also mean that all future valves would be made the XXXX contd:- | ||