As long as the crashes were spectacular I'd watch. That's the only way Nascar gets my attention now.
As long as they didn't double the lap count car speeds as fast as F-Zero would make the race times shorter and perhaps more bearable to watch from start to finish.
What if each vehicle in a race that fast had a camera attached to the front, transferring the footage they see, via radio waves, to a large monitor back in the starting area for the audience to watch the action on. The technical staff of the track occasionally switch between cameras for different moments of the race.
Also, since the races would be shorter than NASCAR then they could put more races in one day at the tack.
In regards to crashes, the drivers would be required to wear special ejector packs that launch them from the driver's seat upon impact, allowing them to parachute safely away from the track.