[Adger Smith]

Comp racing is a very interesting class. I really don't think you could call it heads up. Like everyone has explained it is run off of an "index" and handicaped starts. I don't think index to index is what is traditionaly called heads up.
I know I'm going to catch hell for this, but it is just another form of shoepolish racing.
Instead of having the shoe polish in your hand NHRA does in the form of the CIC. (Competition Index Control) It is a very well laid out application of the CIC by the rules. Go too fast, as the rules dictate, and your index changes. There really isn't any shoepolish, it's INK in NHRA's index books. It is that simple, except it takes a large application of money and a huge amount of work & smarts to be able to go too fast. Go too fast to win a round and you can hurt your chances for the next round, unless your holding power, or worse yet you can hurt your chances of winning in that class until you step your program up. It's the Sportsman version of Pro Stock.