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).
Burnt valves, discussing potential causes such as pre-ignition from spark plugs and engine performance characteristics.
| Identifier | Morton\M22\ img175 | |
| Date | 29th December 1922 | |
| R.R. 235A (200 T) (S H.{Arthur M. Hanbury - Head Complaints} 159 11-8-20) G.{Mr Griffiths - Chief Accountant / Mr Gnapp} 2800 ORIGINAL. RECEIVED TO HS.{Lord Ernest Hives - Chair} FROM R.{Sir Henry Royce} c. to CJ. BJ. c. to RG.{Mr Rowledge} BY.{R.W. Bailey - Chief Engineer} c. to HM.{Capt. W. Hallam - Head Repairs} CY. c. to LP.{Mr Lappin} R1/M29.12.22. RE. BURNT VALVES. X2764 X1812 X3773 I am very pleased you find my fears of close clearance to be unfounded, and that it is difficult to destroy the valves of either Goshawk or 40/50 by the various means you have tried. I agree with your aero experience of pre-ignitions as to the probable cause of the occasional failures experienced. K.L.G. plugs with a cavity might cause pre-ignitions to occur at the commencement of compression stroke, such as would fit in with your suspicions of time of pre-ignition which destroys valves.. I suggest plugs with porcelain like old 4 pointer Bosch would not cause such pre-ignitions. In conclusion I am grateful you find all our valves so very satisfactory, and not fastidiously particular as to quality of steel, clearances, or angles or area of faces. I conclude they are not fastidious from your difficulty in causing damage to them. I notice that the Hawk engine here has six excellent compressions, suggesting that the valves and pistons are extremely gas-tight. This is so necessary for good slow speed running, and for power at slow speeds, but this virtue is the probable reason why our engines shew vibrations caused by slow speed torque re-action. (1) | ||