Sadly its just a fact of indoor sports photography, you generally will be short on ambient light unless the club will like you install your own lights for the pics or use a flash.
Im never overly keen on using flashes at racing events due to the distraction of the drivers. I generally shoot at about 1/200th, iso1600, f4 (my quickest telephoto
) and at my local club I can usually just about get away with it. If you can get faster lenses it really helps, I use a 50 f1.8 occasionally if the light is really bad and I can get close enough that lets me drop the iso down to 400.
*dreams of the day I can afford the 200mm f1.8*