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).
The dispatch of modified bottom tappets and valve springs to resolve a valve bounce issue, with instructions for comparative testing.
| Identifier | ExFiles\Box 108\1\ scan0403 | |
| Date | 23th February 1938 | |
| To Rm{William Robotham - Chief Engineer}/I.M.Waller, Hotel de France, Chateauroux, INDRE. France. 600M Rm{William Robotham - Chief Engineer}/Swd1.11/JH.23.2.38. 26.0.6. We have sent out the following parts which should be fitted in accordance with this memo. (1) 12 Bottom tappets which are modified in the base to prevent the possibility of the push rods jumping out and getting wedged as experienced on one of our units with the existing bottom tappets. (2) 6 valve springs in Swedish wire to EW.1428 which have been made by the Tempered Spring Co. and should be fitted on Nos. 7 - 12 in place of the existing S/CV springs. In order to obtain further confirmation of the period which you say is valve bounce without holding up the car to any extent will you please try the following. (a) With old ¼ dia. push rods and old existing type of tappets check speed at which you term valve bounce occurs. (b) Again check with new bottom tappets and existing 5/16 dia. push rods which give a total weight of 2 ozs. in excess of condition (1) Mileage should be continued in this condition. As stated in your previous memo. tests here show that the valves begin to bounce at 4,300 r.p.m. and if we attempt to run in excess of 4,450 r.p.m. there is continual misfiring and popping in the air silencer. It seems strange that in accordance with your memo. 14/10.2.38. valve bounce should occur at 75 m.p.h. (3850 r.p.m.) and yet it is possible to reach (88 m.p.h.) (4500 r.p.m.) easily under favourable conditions without any | ||