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).
Development work comparing a 'close-centres' cylinder head with a standard one on a single cylinder Bentley unit.
| Identifier | ExFiles\Box 133\2\ scan0113 | |
| Date | 11th December 1934 | |
| Hs{Lord Ernest Hives - Chair}/Wd.{Mr Wood/Mr Whitehead}/CHP.1/GB.11.12.34. SINGLE CYLINDER BENTLEY UNIT. Period covered by this report : - 12th October to 30th November 1934. This engine has completed a further 42 hours, 35 minutes running time since the last report was issued. The work carried out during this period consists of development work on a standard type Bentley Cylinder Head in which the valve centres are altered so as to allow the use of larger valves and also to permit freer gas flow through the valves. This head is built to LeC.4100, and will be known in this report as the "Close-Centres" Head. The running time also includes several power curves taken with the standard Bentley cylinder head, for the purpose of making direct comparisons with the "close-centres" head. The effect of valve timing overlap has also been investigated. ---------- S U M M A R Y. COMPARISON OF "CLOSE-CENTRES" HEAD WITH STANDARD BENTLEY. The "close-centres" head, as shown on LeC.4100, gives a considerable improvement in power output over the standard head, amounting from 6.0% to 8.7% according to the speed, when running with the best all round valve timing and 12° overlap. If the normal Bentley timing is used, the power output of the "close-centres" head is slightly better than standard below 2000 R.P.M. At 2500 R.P.M. there is an increase of 2.6%, gradually improving to 8.8% at 3500 R.P.M. and 15.6% at 4500 R.P.M. With regard to detonation, the "close-centres" head is superior to the standard at all speeds, when operating on | ||