What is the highest number of horsepower one car can have?

What is the highest number of horsepower one car can have?
there is no way to determine the answer to this question. on a given engine, there is going to be a calculated horsepower rating that the engine can make before it fails. every engine is going to be different. type of fuel, number of cylinders, layout of those cylinders, bore (diameter) of the cylinder, and stroke (length of 'up and down' movement of the cylinder) are just a few of the things that factor the horsepower rating.

couple this with the fact that a car can have more then one engine... and in the case of hybrids, you have an electric motor attached to the engine which adds to the overall horsepower rating. so the answer to your question is.... there is no highest number.