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).
Review and opinion on the potential of a high-power cylinder head design compared to alternatives.
| Identifier | ExFiles\Box 134\2\ scan0044 | |
| Date | 18th July 1935 | |
| -3- EB/Ru.15/KW.18.7.35. Bearing these in mind, we review the present position as follows :- High Power Head. We were probably more enthusiastic than anyone else with regard to the potentialities of this head. As a single cylinder unit it has certainly lived up to expectations with regard to power output; it has been found possible to suppress detonation, and the valve gear has been made to operate reasonably well. It is now really for design to say whether it is any good as an in-line engine. Our own opinion is that, since it requires two inlet valves which will have to be operated by a single push rod, it is going to necessitate hydraulic tappet adjustment if the head is going to be in aluminium. We are very anxious to get away from the hydraulic tappet in any new design if this is possible. [Handwritten note: Get away with one] Tan's ramp head three valve head has shown that it is possible to get cylinders having almost as good volumetric efficiency, which will not require hydraulic tappet adjusters. There remain two unknowns about this head which are almost impossible to solve on the single cylinder test bed. One is whether the rate of pressure rise will make the engine inordinately rough, and the other is whether it will slow run satisfactorily. Briefly, it does not seem worth while designing this into a complete engine until we have at least explored its direct competitor, the overhead camshaft engine. | ||