Cool Hardwarez has written a great guide on How To Make A Front Blowhole. Heres a Quote:
We usually slice up our IDE cables and round them up to leave ample of space for air to move around. But is that efficient enough ? Heck no, that's just a lil' something to ease your mind that your casing is having proper air flowing around the hardwares. Honestly, there is nothing much you can do to stop the heat from generating but we can still do something about it. We can "cool" the hot air inside the case by sucking in cool air.