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).
Attempts to cure valve spring surge and valve bounce on the Vulture Automatic Tappet Cylinder Head.
| Identifier | ExFiles\Box 123\3\ scan0170 | |
| Date | 1st April 1934 | |
| X4704 April, 1934. Report on further attempts to cure trouble due to Valve Spring surge and Valve bounce on the Vulture Automatic Tappet Cyl. Head. To cure this trouble it was decided to try the following - (1) Changing the present camshaft (standard E.82448) for the old standard one (E.80070). (2) Changing the valve springs as fitted to Vulture head (E.84551 & E.84552) for a set of higher rating springs to Hs.{Lord Ernest Hives - Chair}1302. Accordingly a camshaft to E.80070 was fitted to P.II No. 7 Engine Unit, and the Vulture Cylinder head (fitted with springs to E.84551 & E.84552) fitted and run up to 3600 r.p.m. before any trouble was experienced - above this speed the trouble due to valve bounce began to be felt. The valve springs were then changed for springs to Hs.{Lord Ernest Hives - Chair}1302 - these ran satisfactorily as far as we thought it safe to run the engine; i.e., 3700 r.p.m., without any signs of valve bounce. Owing to lack of time, this cylinder head being needed for 28-EX car, it was impossible to compare these springs with the present standard camshaft E.82448. Note: During the course of the tests, No. 3 Connecting Rod broke at 3600 r.p.m. Power curves showing the difference in max. power obtainable with the two camshafts (E.80070 - old standard; and E.82448 - latest standard), using present standard compression ratio, and carburetter on NO. 7 large bore unit, are attached. | ||