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).
Troubleshooting issues with self-adjusting tappets on a Phantom III engine.
| Identifier | ExFiles\Box 146\3\ scan0202 | |
| Date | 5th December 1936 | |
| 1245 W/P. To Sr. from Rm{William Robotham - Chief Engineer}/Swdl.{Len H. Swindell} Rm{William Robotham - Chief Engineer}/Swdl.{Len H. Swindell}2/AP.5.12.36. PHANTOM III. SELF ADJUSTING TAPPETS. In reply to your memo Sr/VA.4/ET.2.12.36., the diametrical clearance between the plungers and the casings should be between the limits of .001" and .0012". This clearance has not been altered since Production of Phantom III. commenced. With regard to the trouble of the valves being held off their seats after running, we assume that when you first start the engine the valves are seating O.K. and that you have no misfires. In this case, it is unlikely to be anything to do with the plunger clearance in the case, unless the plunger is actually binding, as it is when the oil is cold on first starting that plunger clearance enters into the question of valves being held open and for this reason we have recommended Mobiloil Arctic for the winter on account of its low viscosity at low temperatures. It is unusual to have this trouble when the engine is warm, we give however some of the possible causes - (1) Plungers actually binding in the cases, this you can detect from the condition of the plunger surface. Any roughness to be lightly removed. (2) Inner or outer valve spring failure or collapse. (3) Dowel pin which retains the thrust washer on the eccentric broken off, or cracked eccentric which occasionally occurs when the dowel pin is driven into the eccentric during assembly at the Works. This causes binding on the bronze bush. (4) Insufficient float on the rocker shaft as controlled by the distance piece between each pair of eccentrics. The distance piece should be perfectly free and as a minimum it should be possible to get a .004"-.006" feeler between the distance piece and the eccentrics This trouble sometimes occurs if the rocker shaft is removed and not checked for the above when re-fitted. (5) Look for signs of binding on the floating bush between the actual rocker and the eccentric also continued | ||