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).
Letter from Chrysler Corporation to W. A. Robotham regarding exhaust valve temperatures and engine performance.
| Identifier | ExFiles\Box 158\4\ scan0284 | |
| Date | 19th December 1938 | |
| 1360 CHRYSLER MOTORS STANDARDIZED QUALITY CHRYSLER CORPORATION Detroit, Michigan, U.S.A December Nineteenth 1938 Mr. W. A.{Mr Adams} Robotham Rolls-Royce Ltd. Derby, England Dear Mr. Robotham: I wish to thank you for the compliment inferred in your letter of December 2, in that you thought that I could answer the various questions you asked; however, I will do my best to answer them. We believe that a side exhaust valve will run hotter than a corresponding overhead exhaust valve with the same M.E.P., because in a side valve only about two-thirds of the valve is in actual use for the passage of gas which must cause higher velocities and greater wire drawing, and also because of the difficulty in cooling a valve seat which is on the under-side of a shelf, so that the steam bubbles will tend to gather and not move upwards bringing in cooler water. Our experience indicates that not only hot exhaust valves make their presence felt by the engine continuing to run after the ignition is switched off, but that other hot spots such as spark plugs or corners in the combustion chamber can be serious offenders or offenders in conjunction with a hot valve. We believe that the long cooled exhaust valve guide is the most practical means of controlling exhaust valve temperature. At the present time, we are using a distributing water pipe in the block with water jets directed at the exhaust valve seats which seems to produce a material reduction in temperature, as demonstrated by a smoother running engine. We do not know about the effect of the exhaust valve head influencing the scrubbing action of the gas but have found that "T" headed valves with high valve guides work better than "tulip" valves with low guides. I believe a test will show that the average temperature of the gas in the exhaust port is greater than the average temperature of the gas in the combustion chamber. We have found that the exhaust valve temperature is extremely sensitive to port shape and that any improvement in the free flow of gases will have a very marked | ||