Increasing blow-down time produces more peak horsepower and the engine will have a greater RPM potential. This can be accomplished by slightly raising the exhaust port, or by widening the exhaust port at the top of the port. Widening the top of the port doesn't necessarily increase blow-down "time" but, it does create a more efficient exhaust, which is needed with all the inlet/intake mods. What goes in must come out. However, I wouldn't advise doing it if you have not experimented with it. Here are a few before and after pictures. These are NOT professional ports. It's just what I do to my own engines along with block mods for drag racing. Some of the "after Pictures" are before I finished them, so there's shavings. They work. Sorry for not reducing the size of the pictures.