My system has a corsair h75 installed and a 4790k cpu at stock 4.00 but under steps tests of loads at 90-100% it gets to 85-90C. Why are my temps so high?
What case are you using? How many fans do you have? Anyways, this is normal Temps especially at full load these stress tests push your CPU to the limit otherwise you shouldn't encounter these Temps in normal Circumstances.
the H75 isn't a very high end cpu cooler you should invest in a thicker 120/140mm rad or get even better cooling and invest in a 240/280mm rad or go with aircooling