If you don't know what you're talking about don't post.
It takes 4 EVs to make a stat, HP is based off of IVs (Individual values), and the Serebii pages are full of errors at present. Not to mention there weren't any such thing as EVs in G/S/C.
A poke's IVs are hidden values ranging from 0-31 that are randomly assigned to a poke when you encounter it (In the first two generations [that includes Crystal], these values were from 0-15 iirc). A poke will retain these values for as long as you keep the game (as in, they never change). For each IV it has, it gains an additional point in that particular stat by Lv.100. Hidden Power is based off of IVs, making it completely random from poke to poke, and impossible to change a particular poke's HP. Catching another will get you new IVs, and probably a new HP.
Just use Rock slide though since it's ingame.