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).
Results of tests conducted on Wraith Car 25-C-VI to achieve 100% slow running and good idling.
| Identifier | ExFiles\Box 6\6\ 06-page214 | |
| Date | 7th June 1937 | |
| To E.{Mr Elliott - Chief Engineer} c. to Hs.{Lord Ernest Hives - Chair} c. to Rm{William Robotham - Chief Engineer}/Sdl. c. to RM{William Robotham - Chief Engineer}/Ch. c. to Rm{William Robotham - Chief Engineer}/st.{Capt. P. R. Strong} 600 Rm{William Robotham - Chief Engineer}/Sym.6/JH.7.6.37. Wraith Car 25-C-VI. We have just completed a series of tests on the above car with the object of producing 100% slow running and good idling. Without going into all the details of the various tests carried out, we give below the results arrived at from those tests. (1) Tappets must be set at .010" inlet and exhaust or, the present camshaft EX.24286 must be modified to give similar conditions when the tappets are set at .004" inlet and .006" exhaust. (2) PLB.30X sparking plugs to be set with a .030" gap. (3) Peregrine type distributor head and rotor to be fitted to prevent spark from arcing between rotor blade and distributor body when using .030" plug gap. (4) Delco coil to be fitted to cure misfires on pick-up. This coil has up to now proved better than the latest R.R. coil E.73673. (5) Separate idle feed on the carburettor. This has given us better slow running than the original standard carburettor, and has entirely cured spitting back in the silencer. Further experiments however will have to be carried out because of any other troubles, such as poor consumption, which we may have run into with the separate idle feed. (6) Modified governor advance curve characteristic to enable ignition to be set at T.D.C. Any reduction of tappet clearances with the present camshaft or reduction of spark plug gap, has a detrimental effect upon slow running. Rm{William Robotham - Chief Engineer}/G.H.Hyman. | ||