High heat means you'e either running lean or the engine is being run under heavy load, such as with sticking brakes or through tall grass, or even at WOT for far too long.

I've hit almost 400degF with one of mine due to running too lean and too long through tall grass. Didn' hurt it, but I cna't say that's always the case.

Check your vehicle for any binding parts, richen the HSN on your engine by at least 1/4 turn, don't stay on the throttle for extended periods and stay out of tall grass.