Actually your title says "want to 4 mil." Meaning you could want a 4 mil crank, you have a 4 mil crank and need new connecting rods, want to build a 4 mil cheap, and so on. As stated above you will want an actual 4 mil crank, a cool head or a noss head with cut domes, and increase your timiing. You will need to port your cylinders since your port timing will change with the new crank. Good luck!