Add some leg power

my mechanics are pretty well sound but i am not getting a lot of velocity and i wanted to add some leg power (like tim lincecum). I need more leg power because i am not that big.

What are you asking?

how to get more leg power, like tim lincecum etc.

If your mechanics are pretty well sound then you would be using your legs and generating velocity.

So maybe you should get somebody to look at your mechanics and see what they think.