Hey Deb - fortunately, this question was answered several times in the last several years. Unfortunately, many of those posts disappeared with the forum ownership changes, though a few
like this still survive. I haven't found the ones where the additional expertise of the thermodynamic engineers and the extra charts and graphs are located, but much is still covered in the link above.
In a nutshell; using stuff like the
graph mvannote posted earlier and others, you can see the "sweet spot" for temperature versus wear, power, mileage, and emissions. This temperature for most engines like ours, and in street use, lies roughly between 175 and 185 degrees
during operation. The thermostat rating (cracking temperature) stamped on the thermostat must be lower to achieve that
operational coolant temperature range. A 160 to 170 thermostat will generally achieve this, and is likely why yours has one.
There are pros and cons to every temperature, and for example, if you want to reduce emissions you should raise the temperature above this point. If you want increased mileage and reasonable power, stay in the sweet range. If you are after max power, at the cost of some mileage and emissions, operate below that range.
One caveat not often mentioned is the temperature the engine is broken-in and worn into already. As the engine changes temperature, the dimensions change with it, and operating permanently at a new temperature will experience a new 'break-in' period. During this period, there will be greater wear as the parts establish their new seating and wear patterns. There are additional negatives, such as increased carb fuel boiling and vapor lock issues that follow higher temperatures. So, I generally suggest not changing the current temperatures on a used/ broken-in engine, unless the reasoning and benefits are strong. Hope that helps.
David