Abstract: A getter selected from the group consisting of zirconium, hafnium, yttrium, and mixtures thereof is used as an additive for metal coolants, e.g., sodium, potassium and sodium-potassium alloys, in metal cooled internal combustion engine valves.

Abstract: A valve stem retainer provides improved frictional engagement between the retainer segments and the valve stem. The retainer includes a pair of retainer lock segments, each of the segments having a radius of curvature less than the radius of curvature of the valve stem on which the segments are installed. The segments are expanded by deformation elastically into conformity with the valve stem and when so installed, provide tight frictional engagement with the valve stem. The segments define, in a first position on the valve stem, a pair of diametrically opposed gaps along a portion of the periphery of the valve stem. For the improved results of the present invention, it was found that the ratio of the width of the pair of gaps to the radius of the valve stem should be carefully controlled.