Current testing requirements for high temperature alloys are defined in general industry specifications (ASTM, AMS), as well as in user specifications. Many of these requirements were established in the 1960's when production practices were yet to be refined.
cowling - protective covering consisting of a metal part that covers the engine; there are powerful engines under the hoods of new cars; the mechanic removed the cowling in order to repair the plane's engine.
An overhead valve engine (OHV engine) is an engine in which the valves are placed over the cylinder head. This was an improvement over the older flathead engine, where the valves were placed in the block next to the piston.