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).
Issues with over-oiling on the Wraith and valve sinkage on Wraith, 25/30 HP, and Bentley models.
| Identifier | ExFiles\Box 131\3\ scan0098 | |
| Date | 22th June 1939 | |
| - 3 - 3. Over-oiling on Wraith Trouble has been experienced with plugs oiling up on cars in service due to oil getting down the inlet valve stems. Investigation has shown that the oil collects in the recess of the top spring retaining washer and then seeps down the stem through the slots of the taper cotters. The trouble can be cured by stopping up the oil holes in the valve end of the rockers, as has been done on certain Wraith cars at Depots, but, as this may result in wear of the rocker and valve stem, it was considered better to evolve means for preventing the oil going where it was not wanted rather than to cut off the oil altogether. We have therefore experimented with various sealing washers which fit over the end of the valve stem, and we are now satisfied that very good results can be achieved with a soft aluminium washer suitably domed before fitting so that when flattened out in position it fits firmly into the recess of the top washer. It does not become dislodged with running, but is easily removed when desired for decarbonising etc. A Depot Sheet is being prepared instructing this modification on cars in service. Provision is being made on B.5 so that the same scheme can be fitted on Production if desired. 4. Valve Sinkage. Wraith, 25/30 HP, and Bentley It has been rather disconcerting to find that, after running 18,000 miles on the present cylinder head on 27.G.VI without any trouble with the valves, exhaust valve sinkage has developed during the last 7,000 miles, but has only become noticeable during the last 2,000 miles, one particular valve having lost clearance at the rate of .004" per 1,000 miles, thus upsetting the slow running. The cylinder head has now been dismantled, and it is found that No.1 exhaust valve seat had sunk approximately .030", and No.2 about .010". The remaining exhaust valves are quite good with only very slight signs of sinkage. This trouble has been with us on the 25/30 HP. and Bentley, certain cases on the 25/30 HP. having been very acute, with sinkage of as much as .060" in 8,000 miles. (continued) | ||