I've got a 91 305 and it heats up to a little more than 180 and stays there. My fan doesn't come on till 235 (I think) so it'll heat up if left idling or sitting in traffic and I've noticed that it runs way better at 220, noticeably more power and a much better deeper growl and it feels smoother and the gas peddle is stiffer.
After a small amount of driving it, it'll cool back down and go back to being the slow tired old 305 that it is but my question is if my car runs better at 220 why is it set to run at 180? (Everything is stock). Is it harmful to run it that hot for long periods of time? Could I get a 200 or 220 thermostat and fix the issue?

 

If its stock its not set to run 180. Should be closer to 195-200 with fans turning on over 220

As far as running better thats hard to judge without actual dyno or track performance. There could be some spark and fuel changes occuring at high temps that it may like more. Wont know without datalogging and measuring power via dyno

 

With cast iron heads, optimum combustion occurs around 220-240 degrees. Hence why the fan doesn't turn on until 235. Some people in hot climates have issues though where that is too hot. However that is usually due to heat soak in injectors or ignition components, fuel temps getting too high, from sitting in traffic for too long. So, yes, your car should be running better and have more power at 220 than at 180.

 

No, it's designed to run that hot, you probably have a lower than stock rated thermostat or none at all. 180 degrees without the fan on is pretty low for June. I would try a 180 degree thermostat and work my way up to a higher one if you still don't like the temp it's at. Being too cold it will run a little sluggish and not burn all the gas, but if you go too high and it starts overheating while in heavy traffic, that could potentially be bad.

 

Heat expands everything. Motor stock clearances are set to run at the stock temps. Running colder, clearances are off. Hot motor, cold air. Actually this crap comes from , (I assume) the many years Hypertec sold those thermaster chips with 160 thermostats and all the rage was running at 160. Truth be told you motor wears out faster at colder temps. Actually general temp aftermarket motor anything over 180 you should be fine. Stock Id stick to the stock temps.