Brake horsepower per cubic centimeter or (bhp/cc) is a figure of merit that is used to indicate the 'state of tune' of an internal combustion engine.
It is defined as the ratio of the engine's net power output to its displacement, the internal size.
Power is measured at its rated speed and full throttle.
Power density may also be considered similar, although this is usually stated in terms of the engine's external overall size, rather than its internal.
A 'typical' car engine, of around 1980, would be considered 'highly tuned' if it delivered more than 100 bhp/litre.