If you're doing oil changes and checking plugs after every few races, feel free to go a little cooler, like 160. It might free up a few ponies with the proper fuel trim.
Otherwise, 180-190 is fine, and as long as things are getting up to temp for a while. The main concern is oil health and ring health. If the engine doesn't get up to temp, the junk in the oil won't evaporate off, and the rich fuel mixtures associated with cold engines wash down cylinder walls which can dramatically shorten ring life.