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).
List of technical modifications and corrections for an engine unit regarding valve springs, push rods, spark plugs, filters, and carburettor settings.
| Identifier | ExFiles\Box 91\1\ scan0045 | |
| Date | 8th August 1935 | |
| -2- (2) With the latest 8:1 eccentric tappet ratio, we can run with slightly weaker valve springs and the combination we now wish to adopt and which we have fitted to this unit are Hs.{Lord Ernest Hives - Chair}1827 outer springs and E.86364 inner springs. (3) Steel push rods are not satisfactory due to the difference of expansion to that of the aluminium cylinder block and head, and consequently holding the valves off the seats when the engine has cooled down. These should be replaced by the strengthened duralumin rods Lec.4626, and until these are available, by the original dural rods E.85322. (4) Sparking occurred between the inlet spark plug terminals (Chater Lea) and the cylinder recesses with RL-14 plugs which are the proposed type for SpectreCodename for Phantom III. This was overcome by fitting a longer plug, RR-14, but West has a new type of terminal which should be fitted in conjunction with RL-14 plugs on other units. (5) The Tecalemit filter in this unit is not the correct type and should be replaced by one of the original design, E.86454. (6) The floatchamber level setting should be .650 from the parting surface under a 2 lbs. pressure. -25 Drawing limits should be tightened up as carried out for the 25 HP. carburetter. The slow running jets are reduced from .025" to .020" dia. and are to Hs.{Lord Ernest Hives - Chair}1991. Control pins foul the floatchamber before the full strong position is reached; it is essential that the pistons will drop definitely on to the bridge in the strong position for starting. Hs{Lord Ernest Hives - Chair}/L.H.Swindall. | ||