Nitro Engines - (or glow engines) are great! They are small and make lots of Horsepower (HP or BHP). They come in many different sizes (displacements) for the different modelers requirements. For example in or out board mounted. Engines up to .32 are available with a pull start. They run on 10-60% Nitro laced fuel designed especially for Radio Controlled models. Engine size is measured 2 ways; by cubic centimeter (7.5cc) or cubic inch (.46 cu.in.). So a .10 engine (1/2HP) is small compared to a .90 engine (5HP).
Nitro engines can turn very high RPM and should be carefully handled and maintained from any contaminants (dirt & water) getting into the engine. However, the engines are easy to rebuild too.