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).
Sticking valve inlets on the 20 HP engine and Phantom power curves.
| Identifier | ExFiles\Box 106\5\ scan0033 | |
| Date | 17th October 1928 | |
| To E.{Mr Elliott - Chief Engineer} from Hs{Lord Ernest Hives - Chair}/Rn.{Mr Robinson} X5060 Hs{Lord Ernest Hives - Chair}/Rm{William Robotham - Chief Engineer}8/LG17.10.28. With reference to our telephone conversation of yesterday. Reports on most of the points will be coming through, but briefly the information you asked for is :- (a) 20 HP. VALVE INLETS STICKING. These inlet valves have the clearance cut down to .002". They have more oil than standard, as they should get a squirt of oil each time the valve is at the top of its lift. Reduced valve guide clearance helps us with silencing the valve gear. We have run 10,000 miles without trouble on the Phantom with reduced clearance. Perhaps we have not got the 20 HP. lubricating proportions right yet. Perhaps the 20 HP. valves at WW. are gumming up through absence of speed work. Perhaps the oil consumption is high and they are carboned up. We have run a long way with reduced clearance without trouble. (b) PHANTOM POWER CURVES. Y771 V.{VIENNA} series onwards compression ratio was about 4.15/1. F2B. series with the turbulent head was 4.25/1. Experimentally we shew a slight gain in power, on production they do not. 'SS{S. Smith}' engine fitted up with 116° camshafts and std. carburetter with 4.5 comp: ratio only shews a gain of 10 HP. over standard at 2500 r.p.m. 15 HP. at 2750 r.p.m. i.e., the curve of the 'SS{S. Smith}' peaks at a higher r.p.m. With the Claudel carb. we get a further 9 HP. at 2750 r.p.m. or 132 HP. Considering the small compression ration increase the 'SS{S. Smith}' does very well with the standard carburetter but contd:- | ||