THE trend in poppet valves during the past year, like many other advances in science, Mr. Colwell points out, has been an improvement upon existing performance, rather than an entirely new development. To effect a steady improvement in existing designs, the study of fundamentals, such as grain flow, structure, forging temperatures, coolants, and interior construction, has been resorted to, and thorough research on valve steels has been carried out, he reports. In the study of valve steel, 300 analyses were examined; intensive work was done on 20; and 4 showed definite merit, he says.
Grain flows in aircraft valves made by the extrusion and gather-upset processes are compared. Results of an investigation of sodium cooling and head designs of aircraft valves by means of glass valves are reported and illustrated. Four outstanding automotive valve steels are analyzed chemically and physically - Silcrome No. 1, Silcrome XB, Silcrome X-10, and Silcrome XCR. Mr. Colwell also discusses rotating valves, sticking valves, valve guides, grain flow, valve-seat inserts, valve retainer locks, “superfinish,” and surface treatment.