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).
Engine performance tests with a special fuel blend, including issues encountered and modifications made in preparation for the Le Mans race.
| Identifier | ExFiles\Box 82\4\ scan0379 | |
| Date | 1st October 1936 | |
| -2- Results. Special petrol was used for the first test, made up as follows - 50% Benzol 30% Methanol } Tested at 8.5 : 1 comp. ratio. 20% Aviation 680) This combination having been found most suitable for high power work on this type of engine. There was no audible detonation anywhere in the speed range, running full throttle. Prolonged running at high speeds, however, the engine could be run switched off, and hardly any difference could be noticed. This was proved to be due to auto-ignition caused by poor water circulation round the combustion chamber. Coupled with this was the fact that the exhaust valve guide bosses had been machined away partly, and the valves were getting far too hot. This was proved by spraying water on the valves by small pipes taken right up to the valve stems inside the exhaust ports. An improvement resulted (30%) in the switching off at high speeds characteristics. The cylinder head was then cleaned up in the water passages by hand, quite a lot of surplus metal being chiseled out. A distinct improvement was noted in the overheating at high speeds. During these preliminary tests the pistons were periodically examined, and it was found that cracks were developing in the webs below the crown. The pistons were modified by putting in two extra webs, joining and crossing the existing two webs of the standard piston. A series of endurance tests was then started to determine the life of valves and seats under these conditions. The curve B.V.96 shows valve stretch plus pocketing or hammering of the seats into the head, during an endurance run of 18 hours. See separate report Hs{Lord Ernest Hives - Chair}/Swdl.{Len H. Swindell}11/JH.20.5.36. At this time we were particularly interested in the life of the valves, etc., owing to the entry of the car for "le Mans" 24 hours race in France, the date for which was getting very near. | ||