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).
Camshaft tests and cylinder head development for Bentley and 25/30 engines.
| Identifier | ExFiles\Box 82\4\ scan0387 | |
| Date | 1st October 1936 | |
| -10- Hs{Lord Ernest Hives - Chair}/CTS.{C. Trot Salt - Carburation}16/KW.1.10.36. The conclusions to be obtained from the camshaft tests do not give much of a clue towards making a new shaft to give increased output, but they do agree to some extent with the line of development that we intend to adopt on both Bentley and 25/30 engines. It is a known fact that most of the resistance in the breathing of these two engines exists in the ports, especially in the case of the Bentley. A cylinder head is almost ready for test, which is in effect the head EX.22594.A. used in this year's T.T., but having a Comp. Ratio of 6.5. The inlet ports in this head are increased in area by nearly 45% over the present standard head. Allowing for the lower comp. ratio, (air standard efficiency formula) we expect an increase in power of 17% over the present production Bentley. As mentioned in the report, big carburetters on a large induction pipe were used on the T.T. engine. The mixture strength was cut down to absolute maximum economy for the race, and the petrol consumption was actually about the same as that of the 3 1/2 litre engine in the 1935 race. As would be expected on a large bore pipe, under these conditions, snap acceleration was very poor at low speeds. This factor was not very important, however. Also, it should be mentioned that the engine would not run evenly below about 750 R.P.M. light. The outcome of this, however, for a production job should be that a shorter duration camshaft could be used than present standard, and combined with the present bore induction pipe on production, tick-over should be greatly improved, while the present maximum B.H.P. should be maintained of the standard engine. Hs{Lord Ernest Hives - Chair}/C.T.Salt. | ||