Stay with the 180 thermostat...echo to what hotrod Lincoln said. Also temp fluctuation is the thermosta opening and closing. If temp goes up and stays up or climbs higher....then you have overheat issues. Also,because of tighter clearences new/rebuilt engines will run a bit hotter until they break in. The test of effective cooling will be when you drive it.as in how does it cool on hot days, cool on hills, in town traffic etc.
