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 Studebaker Corporation discussing exhaust valve temperatures, cooling methods, and engine flare-up issues.
| Identifier | ExFiles\Box 174\2\ img299 | |
| Date | 14th December 1938 | |
| PLEASE MAKE 6 COPIES THE STUDEBAKER CORPORATION SOUTH BEND, INDIANA December 14th 1938 Mr. W. A.{Mr Adams} Robotham Rolls-Royce Limited Derby, England Dear Robotham: Although we do not have comparative test data, I do not believe that in present-day engines the exhaust side valve will run hotter than the corresponding overhead valve. As you know, the use of tubes to carry the water from the pump and distribute it near the exhaust valves has become quite common in recent years and I believe that, with this method of cooling, it is possible to keep exhaust valve temperatures down to values no greater than are obtained in the overhead valves. As far as means for cooling valves other than the use of the sodium cooled type are concerned, we have found that considerable could be accomplished by an increase in valve stem diameter and, as you have mentioned, by increased length of the valve guides. However, increasing the length of the guide is generally considered to be effective only if the guide is water-jacketed for nearly the full length. In other words, increasing the projection of the guide into the combustion chamber in some instances has been reported as being detrimental rather than an advantage. As for the shape of the exhaust valve head having an influence upon valve temperatures, we have seen no evidence of this or any effect due to port shape. However, we have not done any considerable amount of work along that line. The same holds true for the hydraulic lash adjusters. There is not much question but what reducing the time during which the valve is closed will tend to increase its temperature and it is reasonable to believe that the shorter time that the valve is on the opening ramp with the hydraulic adjusters is of some benefit. However, we have not found any evidence that there was a major difference due to this. I infer from your questions that you may be experiencing trouble from the tendency of the engine to continue running after the ignition is switched off. We have had occasional flare-ups of trouble from this source and have found that, although it was influenced by valve temperature, the factor which appeared to be of most importance was the mixture in the manifold at the time that the engine was shut down. For example, a certain amount of trouble of this sort occurred shortly after the adoption of the downdraft manifold and there had been no other change in the engine which would account for this trouble. Checks made on a particular engine with both the downdraft and updraft indicated that it was the mixture in the manifold that was making the difference rather than any change in valve temperatures. In other words, | ||