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 Lycoming Manufacturing Company detailing methods for improving engine volumetric efficiency and reducing exhaust valve temperatures.
| Identifier | ExFiles\Box 174\2\ img297 | |
| Date | 6th December 1938 | |
| PAGE 2 DATE -Dec. 6, 1938 LYCOMING MANUFACTURING COMPANY, TO Mr. W. A.{Mr Adams} Robotham On engines in which we expect the maximum out-put we use a venturi shaped intake port, and on the under side of the valve on the radius. This combination gives us very excellent volumetric efficiency. One point which I over-looked in regard to exhaust valves, and which is something we do to reduce valve temperatures that is not done in general practice, is our method of machining the valve guide. We run the valve guide up to within 7/8 or 1" (depending on design) of the top of the cylinder, and the top of the valve guide is counterbored with a straight counterbore and sharp edge cutting tool about .020 larger than the normal diameter, having a depth exceeding the life by approximately 1/16 of an inch. In this manner we shield the exhaust valve stem from the flame, to a greater degree, and also shield the part which operates in the bearing portion of the guide, there being no direct contact with the exhaust flame. With this construction we have been singularly free also from valve sticking and maintain quite normal clearances. While the information given above merely consists of a number of small details I think they are all quite important in getting the utmost out of an engine, and while you are no doubt thoroughly cognizant of these things I merely outline them as being practices which in our experimental work we have found to be very helpful when striving for out-put. With best wishes for a happy holiday season, We are, Very truly yours, E.{Mr Elliott - Chief Engineer} D.{John DeLooze - Company Secretary} Herrick E.{Mr Elliott - Chief Engineer} D.{John DeLooze - Company Secretary} Herrick, President, LYCOMING MANUFACTURING COMPANY. EDH:H | ||