The head heatsink is the main part on a nitro or gas engine that dissipates the heat from the engine block. The full-size auto equivalent is the radiator and water pump that circulate coolant through the engine block to keep it from overheating. On nitro engines there are ways of regulating the temperature by means of tuning the carburetor to lessen or increase the amount of fuel that it mixes in combination with air (leaning or richening).
The ability to disperse heat through regulating the fuel/air mixture thus controlling the engine temperature is one of the few advantages that nitro or small scale gas engines have over electric motors.
