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).
Research into an Overhead Camshaft Engine, comparing it with side-valve and push-rod designs.
| Identifier | ExFiles\Box 113\5\ scan0195 | |
| Date | 2nd August 1937 | |
| SECRET. By.{R.W. Bailey - Chief Engineer} from Rm.{William Robotham - Chief Engineer} c. Hs.{Lord Ernest Hives - Chair} c. Da.{Bernard Day - Chassis Design} c. MX.{John H Maddocks - Chief Proving Officer} c. REC. 1004 Hml/R.2.8.37. O.H. CAMSHAFT ENGINE. About 18 months ago we began to suspect that the in line push rod head, as fitted to all our production car units, was in danger of being beaten by the side valve engine with regard to power output. Since then a visit to America has confirmed that this is so. The side valve engine is inherently lighter and less costly to produce than the push rod type. Two alternatives were, therefore, open:- (1) To follow current American practice and adopt the side valve construction. (2) To endeavour to develop an alternative to the in line push rod engine which would be little or no more costly to produce, but which would develop greater H.P. per c.c., and at the same time lose nothing in smoothness of operation. If we had not acquired the Bentley business, we should be inclined to recommend the side valve as being more suitable to Rolls-Royce requirements than any other type, because a large engine of moderate output is always pleasanter to ride behind and less costly to maintain than a smaller engine from which the same horse-power has been extracted. However, in order to run the Bentley and 25/30 with the same unit, it is of value to have an engine which can be run detuned or with a high specific output. For this reason research was undertaken. The two types of cylinder head selected as possible were:- (a) The overhead camshaft. (b) The overhead inlet side valve exhaust. Personally, we have always favoured the latter scheme because there is no drive difficulty, it appears to | ||