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).
Deterioration of slow running in the Wraith model caused by incorrectly seating inlet valves.
| Identifier | ExFiles\Box 158\4\ scan0233 | |
| Date | 27th May 1938 | |
| 1360 also 654 By.{R.W. Bailey - Chief Engineer} from Rm.{William Robotham - Chief Engineer} c. Hs.{Lord Ernest Hives - Chair} c. RHO. c. Mx.{John H Maddocks - Chief Proving Officer} c. Da.{Bernard Day - Chassis Design} Rm{William Robotham - Chief Engineer}1/R.27.5.38. DETERIORATION OF WRAITH SLOW RUNNING AFTER ROAD USE. The attached report Rm{William Robotham - Chief Engineer}/Swdl{Len H. Swindell}4/R.26.5.38. summarises the trouble caused by inlet valves seating incorrectly. It is a peculiar fact that hard driving, or test bed endurance, does not emphasise the trouble as much as a customer's type of average road running. We understand that 25 heads have been completed. The decision as to whether or no it is necessary to replace these heads can be taken after we have had more experience with Sg{Arthur F. Sidgreaves - MD}'s and Hs{Lord Ernest Hives - Chair}' cars. As far as we can ascertain, castings that have not been machined can be made to take the smaller exhaust valve without difficulty, and this involves neither cylinder head nor valve scrap. Our recommendations for production are, therefore, as follows:- (1) Heads already machined. Fit as produced. (2) Heads not machined. Modify machining of throat to leave more metal between valves. (3) Heads not cast. Modify port cores to leave slightly more material on than (2) for immediate requirements. (4) General design improvement at this point, which can be brought in when it has been thoroughly tested. We are just completing tests to ascertain if we can reduce the size of the exhaust valve without losing power. If we can, a smaller exhaust valve will be combined with recommendations (2) and (3). Rm.{William Robotham - Chief Engineer} P.S. Detail drawing of the way existing castings can be machined and any further castings produced will be completed this week. | ||