What race, how far is the ride? Is it supported (ie, race officials providing water, emergency assistance, etc)?

Hopping in the car at 4am and driving 4 hours out and 4 back is one thing, but when you add physical exhaustion following a long race, that might make for a really long day. Additionally, if I were your parents, I'd be worried about what if something happened and you (being a minor and all by yourself) needed some assistance....either on the drive or the race. Do you know anyone nearby that you could stay with the night before who might shuttle you to/from the race? How about just a friend who would go with you and maybe drive back?

That being said, 17 year olds have convinced parents of worse things...when I was around your age, I managed to convince my parents to let me get a tattoo