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).
Specifications for the Bentley 111 cylinder head and valves.
| Identifier | ExFiles\Box 99\1\ scan0109 | |
| Date | 7th October 1937 | |
| E.{Mr Elliott - Chief Engineer} Dept. (crossed out) c. to Rm.{William Robotham - Chief Engineer} c. to HPS.{Horace Percy Smith - Experimental Factory Mgr} (crossed out) 200B DA.{Bernard Day - Chassis Design}12/G.7.10.37. 419. BENTLEY 111 - CYLINDER HEAD AND VALVES. It is proposed to use the Four Inlet Port cylinder head for Bentley lll exactly as used for Wraith lll, except that the compression ratio will be 6.5 to 1 instead of 6.0 to 1. This means that the height of the combustion space will be 1.040" instead of 1.175", which will leave the metal at top of combustion chamber .135 thicker than for Wraith lll as it is intended to use the same casting for both engines. The inlet and exhaust valves for Bentley lll are the same as instructed for Led.5867, these are the same as for Wraith lll in every respect, except for their length, which is increased to suit the altered height of combustion chamber. The Rocker Cover for Bentley lll is the same as used for Wraith lll except that the bosses for the Air Silencer Supports are not required. We understand it has been agreed to use the altered valve rocker ratio, giving a .350 valve lift on both the Wraith lll and Bentley lll engines, and if found necessary to return to the .400 valve lift for top power on Bentley lll, an increased cam lift is proposed to obtain this increased valve lift. Before a higher lift cam is used it will be necessary to investigate the maximum scrub line on tappet at changeover point on cam, to see that it does not over-ride tappet face. With regard to the water supply passage in cylinder head for the Wraith lll carburetter hot spot, this will be fitted with a blanking plate when the head is used for Bentley lll, and will be shown on the Inlet Pipe design. The Bentley lll carburetter hot spots are to be fed from the thermostat bye-pass in the cylinder head front water outlet, this will be shown on a design at present in hand. The above information will enable you to proceed with the details for cylinder head, valves and valve gear. DA.{Bernard Day - Chassis Design} | ||