It all depends on how much money you want to spend on it.
how much cc's is a 6.5 hp engine
It does depend on the engine, but I'd shoot a little higher and say headers will give a good 15-30 hp 3 or 4 hp depending on the engine
Roughly 16.5 HP
Around 68 hp
A Judson supercharger can typically increase an engine's horsepower by about 30-50%. For a 40 hp engine, this means an additional 12 to 20 hp, resulting in a total output of approximately 52 to 60 hp, depending on the specific setup and tuning. However, actual gains can vary based on factors such as engine condition and installation quality.
Actually HP can only be estimated . he HP depends on a lot of factors about the motor.
97 hp
Depends on the engine...
Depends on the engine...
120hp
505 HP
Displacement does not correspond to horsepower. A 1500cc engine made in the 1960s was much less advanced, and will not be as powerful as a 1500cc engine made in 2015. Give a specific engine model, and answering this question will be much more feasible