Im not a real big fan of fully bored out engine mods... One thing to remember is that the bigger the bore the lower the rpm's become. It may give more torque but it may bcome lesser on the HP side. The best set up is to have the most over square configuration between the bore size and the length of the stroke. Head works is one of the essentials in getting more hp. Think of torque being how much force a punch has and horse power being how fast the boxer can throw those punches. The time it takes for the engine to coplete the combustion cycle is the enemy. Hotter cams will give the valves a higher lift and longer lift duration taking in more air and fuel into the combustion chamber resulting into a more powerful explosion. Port and polish involves shaving, carving and boring out the ports to make them bigger and make a more direct passage to the chamber so that air and fuel can pass through with more volume polishing makes it air and fuel get in and out quicker. Bigger valves and angled skirts and seats give the same effect of packing in more air and fuel for a bigger bang. Harder valve springs or doubling it eliminating valvle floats when the engine spins fast ensuring good compression so you dont lose power at high rpm. Shaving the head will give you more compression againg aiding in making a bigger bang. Now if you bore out the piston size too much it may give more power down low but the engine would be turning slower. Changing the clutch springs to harder ones should be done too to make the power stick to the transmission. Advancing the ignition will give you more power across the rev range.
