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).
Modification instructions for the 30 HP carburettor to prevent exhaust spitting on overrun.
| Identifier | ExFiles\Box 93\2\ scan0215 | |
| Date | 18th November 1937 | |
| To Hd.{Mr Hayward/Mr Huddy} (FOR DEPOT SHEET.) Rm{William Robotham - Chief Engineer}/GR.{George Ratcliffe}4/JH.18.11.37. 30 H.P. CARBURETTOR MODIFIED TO AVOID SPITTING IN EXHAUST ON OVERRUN RM.{William Robotham - Chief Engineer}467. This depot sheet to replace No.Hd.{Mr Hayward/Mr Huddy}354 withdrawn from circulation. (1) Remove carburettor from engine. (2) Remove floatchamber lid{A. J. Lidsey} and gasket. (3) Cut slot in gasket to Rm.{William Robotham - Chief Engineer}467. (4) Remove idle jet tube No.64 and replace with No.70 which has a hole .035" diameter drilled in top. (5) Remove air bleed adjusting screw and replace with Phantom III blank and also blank off small syphon hole. (6) Remove bottom idle hole plug and increase hole from .028" to .046" diameter through cast iron throttle body. (7) Replace plug with Phantom III control screw and spring. It may be necessary to use a 2.B.A. tap in order to get full range of the screw. Mechanical setting approx. 3/4 to one full turn off seal. NOTE. Do not force screw home as this will damage the taper. (8) With earlier models it will be necessary to reduce the diameter of the idle passage from .140 to .100". This can be done by bushing with brass tubing or carried out by Zenith Carburettor Co.Ltd., Attached Sketch. Rm{William Robotham - Chief Engineer}/G.Ratcliffe. | ||