<div class="htmlview paragraph">Detailed results which may be used for design purposes are presented comparing the effectiveness of alternative methods of piston cooling for highly rated engines.</div> <div class="htmlview paragraph">These results, which have been obtained from rig and engine-running investigations covering a wide range of variables, are not found to be adequately correlated by existing pipe flow heat transfer equations, which are given. Details of how to choose a cooling method are presented.</div>