The Effect of Valve Cooling upon Maximum Permissible Engine Output as Limited by Knock
This is a NACA technical note from 1942, issued by the National Advisory Committee for Aeronautics, reporting how cooling engine valves affected the maximum output an aircraft engine could give before knock. Its pictures are plotted graphs of temperatures and heat removal against fuel-air ratio, plus photographs of water-supply plumbing fitted to a radial engine, so a designer might take from them the restrained look of engineering data plots in grey and black line work.
