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).
Technical memorandum discussing the effect of different valve sizes, camshafts, and carburetter settings on engine power.
| Identifier | ExFiles\Box 13\2\ 02-page134 | |
| Date | 1st September 1931 | |
| -2- Size of Valve. Rm.{William Robotham - Chief Engineer} P20. gives the power obtainable with inlet valves having a throat dia. of 1.680" or approx. 30% smaller than standard. 114° camshaft to L.82448 used with the best timing. Rm.{William Robotham - Chief Engineer} P15. is a comparison of the power output with these small valves and some valves 11% larger than standard having clearance machined round them in the head. It should be noted that this is taken with an earlier timing than Rm.{William Robotham - Chief Engineer} P20. Rm.{William Robotham - Chief Engineer} P19. & Rm.{William Robotham - Chief Engineer} P22 give a direct comparison of the standard and 2" throat valves with the 114° camshaft. We took some curves of the 2" valves before the cyl. head was trepanned out to give them additional clearance and in this original condition they were inferior in power to the standard valve. The effect of carburetter disposition and depression is indicated on curves Rm.{William Robotham - Chief Engineer} P15, 19, 20, 22 and 24. It will be observed that the lower depression scores most after 3000 R.P.M. or 80 M.P.H. on the road. Curves Y.1023 have already indicated the effect of choke size on the twin carb. The slow running of the 114° shaft is equal to that of the present standard shaft. We shall have the camshaft on the road on Monday. Hs{Lord Ernest Hives - Chair}/Rm.{William Robotham - Chief Engineer} | ||