Recent Developments in Poppet Valves

AFTER stating that increased speed, mean effective pressure and piston displacement of engines have made valve conditions more difficult during the last few years, the author recalls the path which development has followed by a brief list of materials and methods of cooling.

Where the stem joins the head is the hottest part of the valve. A shield for this point is shown, also a shroud to protect the end of the valve-stem guide. Cooling the valve increases its life. Salt and sodium cooling are compared, and methods of sealing the coolant in place are described.

The construction and behavior of copper-cooled valves are illustrated and recounted, and a one-piece hollow-head valve is described. Reasons for valve-seat inserts are given.