There are several synonyms that can be used for the term "power cylinder group." The most obvious alternative is "engine block" which refers to the metal casing that houses the cylinders and other components of an internal combustion engine. Another synonym could be "cylinder head assembly" which specifically refers to the topmost part of the engine where the valves and other important engine components are located. Other possible synonyms might include "piston and crankshaft assembly" which highlights two of the most important moving parts in any engine, or simply "powertrain," which refers to all the parts of a vehicle, including the engine, gearbox, and drivetrain, that work together to generate power.