What settings does my nikon d3100 have to be on to take pictures at a race?

Going to a big race today and want to take good pictures while the cars are racing, what settings does my camera need to be on in order for them not to blur?

Added (1). So i have the shutter speed all the way to 1/4000 and the pictures i just took for fun are dark, so i took the iso and went higher and the photo is still dark.am i doing something wrong?

Put it on shutter priority and choose a very high shutter speed, the camera will take care of the aperture. Also, use panning as you shoot the cars; that is follow the cars with your camera as you take the shot.

Use shutter speed priority and set it to 1/1000. If you need some more light, raise the iso

Are you at the Glen? I wish I was there!
1/4000 is way overkill.
1/1000 is probably adequate. If you look closely at the images and they are blurry then raise that even more until they aren't.
You will probably have to raise your ISO. As you look at your images if they are dark, boost up the ISO until they are bright and acceptable.
Have fun!