Usually I shoot in Shutter Priority; with changing light conditions from one point on the track to another this usually nets the best results for me.

EXCEPT for this time of the year on extremely bright sunny afternoons, specifically the last two-and-a-half hours of daylight of so. Then I seem to get wildly different results from shot to shot.

The first 2 shots here were taken just seconds apart, the 3rd was an hour later from the same spot. What are better options to get consistent shots throughout a heat race? (Keeping in mind the speed of the cars and having virtually no time in between shots)

Slow my shutter speed down? (1/500 for these shots)
Switch to manual and find something that looks like it works?
Go to Aperture Priority?

Using the D200 when I'm on the track.

I usually shoot between 300 and 400 shots during this time of day; about 1 in 3 come out good. But once it starts to get darker and on into the night, I'll shoot another 300 to 400 shots and then 4 out of 5 come out good. I'd like to improve the 'keeper' ratio of the late afternoon shots, with the ultimate goal of reducing the number of shots, confident that I've got a couple 'keepers' for each driver.

Thanks for any thoughts and advice

Use manual. As for the bright sun, if you can't get what you want then you have yto change locations. Not always possible but it's that or a lot PP later.
Thats one of the nice things about being at Indy this year, I'll be able to move around as much as I want in the turns so I can get the sun where it won't be an issue. Late afternoon and turn 4 and 1 are in the dark, 2 & 3 are nice and sunny.

JS

I'll give manual a try this week. This is the only track that gives me fits like this; it's situated so the sun is behind the front stretch and the entire back stretch has a very white (and somewhat reflective) fence along it. So we end up with about a 50 foot area in turn 2 and turn 3 to shoot in, or else we fight direct sun or reflected sun.

Of course, it doesn't help that this is the only track around here that starts hot laps at 5 pm and racing at 6; most other tracks are either 6:30 or 7 for hot laps, and racing between 7 and 8. If the press box wasn't so far back from the track, I'd try getting on top of it and shooting from the outside, with the sun at my back.

You could possibly try a filter, are you using a UV(0) filter now? or underexpose by a step or two and see what happens. Sometimes there just isn't anything that will worl though.

JS