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).
Exhaust valve sinkage on the 25/30 HP engine, proposing a modification to the cylinder head cooling path.
| Identifier | ExFiles\Box 100\2\ scan0161 | |
| Date | 6th April 1939 | |
| For Hd.{Mr Hayward/Mr Huddy} c. to GWH{George W. Hancock - Head Chateauroux} (K) STAMP: APR 8 P.M. 1939 EXHAUST VALVE SINKAGE -- 25/30 HP. -------------------------------------- There is an increasing volume of evidence that exhaust valve sinkage and allied troubles have got progressively worse during the history of the 20/25 HP. and 25/30 HP. and the degree of trouble coincides with certain changes which have from time to time been made in the design of the cylinder head. The exhaust valve seats at the front end of the head appear to suffer the most, and it would appear that it is due to inadequate cooling of the seats due to the water choosing a path along the cylinder head which is the easiest, but which is the least effective from the point of view of cooling the valve seats. In order to persuade the water to choose a path closer to the valve seats, we would like the transfer holes between the cylinder block and the head modifying as shown in the sketch herewith. [Diagram Annotation - Left] FRONT [Diagram Annotation - Bottom] DRILL 3 HOLES SHOWN RED .312 Dia [Diagram Annotation - Top] PLUG UP 4 HOLES SHOWN BLUE | ||