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).
The performance and modification of exhaust valves, inlet pipes, and carburetter components.
| Identifier | ExFiles\Box 92\3\ scan0272 | |
| Date | 31th May 1937 guessed | |
| ( 5 ) on the S/SLV exhaust valves. The faces of both the S/SLV and KE.965 exhaust valves were badly burnt, so they were returned to the Works for inspection and 12 new KE.965 exhaust valves were fitted. The valves were not dismantled again during the mileage. The felt pellets allowed a slight leak from the rocker ends as required, and this remained constant throughout the running. N° 10 valve "B" side, exhaust, became noisy at the end of the mileage. Inlet Pipes. LOP. E.88259. New complete to above LOP. incorporating:- E.88370 Induction Pipe Heater. Water Heated Hotspot. The induction pipes showed no weaknesses, and were notable for the ease with which they could be dismantled in comparison with induction system of the standard heads. Carburetter. LOP. E.88115. Existing complete to the above LOP.incorporating the following scheme:- Lec.5335 Stronger Throttle Spring. E.88488 Spring. E.88489 Bracket. No trouble was experienced with sticking of the throttle with the stronger spring fitted. The car was received with 058 main and 060 bye-pass jets as standard. These gave no trouble. It was found at Derby that at full output there was a considerable fall of level. The standard jets are large enough to compensate for this fall in level. A special float with reduced leverage was produced which maintained a more constant level, and enabled smaller jets, 056 main and 054 bye-pass to be used without loss of power. These parts covered 15,000 miles. Any further reduction of jet sizes resulted in loss of power. It was found that it was necessary to set the lever higher than standard to avoid weakness with the smaller jets, i.e. .600" to .620" measured over the needle valve, the standard level being .600" to .625" measured at the pump well. Owing to the slope of the carburetter, this makes a considerable difference, and with the modified parts, the car was more susceptible to flooding on a gradient. The saving of petrol was 1/2 m.p.g. at 45 m.p.h. average. (contd) | ||