190 is the temp to maintain for power; if it gets higher than that the engine starts to run like crap because the pistons are too tight in the bore. What exactly is meant by not hurting anything? You could run a stock iron headed motor continuously at 260 plus and never BREAK anything, but it would wear out a little faster. Try to keep it at 190-200 but if you can't then don't fret it. Too COLD is also to be avoided because then your pistons rock in the bore...