Horsepower at Maximum Rpm
Maximum horsepower does not always occur at maximum rpm (revolutions per minute). It is typical for engine builders to design an engine that reaches maximum horsepower before it reaches maximum rpm. They do this so that when you shift to a higher gear, the engine rpms are still in the power band. The power band refers to a range of rpms during which the engine is putting out its best power. You can analyze the power output of an engine on the dyno, which is in the "Modify Engine" part of your shop. Just click on "Engines", then click "Modify Engine" next to the engine you want to put on the dyno. In the "Modify Engine" part of your shop, you can change various specs on your engine and see the result instantly.
Engine design is completely up to you. If you want an engine that reaches maximum power at maximum rpm, just make it that way. If you have an engine that reaches maximum power at maximum rpm and you don't want that, try reducing the size of the intake air passages. That will make the air move faster through your engine and you will gain power at lower rpms.