cause I love racing 17.5 class and I love the feel of them. Plus i love seeing people's faces when I run faster laps and beat their 8.5 motored car with a stock motored car lol no, im kidding. Im just one of those guys that has run mod motors in the past and i just dont enjoy running them so I run the stock motor. They are just smoother to me and I love the way they run. Plus I like running two classes with the same vehicle. makes those LONG race days not so darn boring!