Indeed it is a long borig afternoon….so hopefully you won't mind my long boring response…
If the engine temperature is at 190\200 with a thermostat of 160, it tells me that the rad is having a hard time cooling your engine in the environment that you are operating it. However, if you are on the highway on hot summer days, one would expect the engine temperatures to rise above normal. And if this is the worst scenario that you are going to experience than what you are seeing is probably OK. But at the other extreme, the engine under normal or even cool day conditions, should fall and stabilize somewhere between 165 to 180 (with your thermostat). If that's not happening, than I would think your rad/setup cannot disperse heat well enough for your engine.
An engine running too cool (constantly) will not reach a temperature that can burn off moisture in the engine. Oil, water and the pollutants of combustion will mix to form sludge and a acid byproduct. An engine that reaches OPTIMAL operating temperature can burn off these pollutants an prevents the building up of slugde and corrosive byproducts.
When the engine manufacturers specify an optimal operating temperature , they take this into consideration as well as the expansion (rate) factor of the materials that make up the engine. Too much expansion and you have excessive friction wear; insufficient expansion and you run the risk of fuel leaking into the oil (via blow-by), diluting it and you end up with a lubricant that can't do it's job...end result is also wear.
So what's the right thing to do?...Always try to operate the engine at the temperature that the manufacturer recommends. If that means changing your thermostat in winter and then back in the summer…so be it. If however, your rad setup is such that it can cool the engine on the hottest of days on the highway and maintain just above normal temperatures, then chances are you won't have to worry about changing thermostats..and 180 will do just fine all year round. That's the case with most cars...but when we start putting bigger "heat pumps" (
) in....then we have to increase our cooling capbilities..i.e. bigger rads, more efficient rads, auxillary cooling fans, etc, etc.
Is the electric fan (2700 CFM) the only thing cooling your rad?
I personally use a flex-o-lite fan PLUS a two stage electric cooling system (1200 CFM and then 2400 CFM). The electric system is most useful if you end up in city traffic. I find that the flex-o-lite fan does a tremendous cooling job at normal traveling speeds…BTW..I use a 180 degree thermostat….and never drive the Camaro between late October through May.
BTW, I would be reluctant to start putting holes in the shroud. Oh , and 2700 CFM is really not as much as you think. I tried running my car with just the electric fan running (2400 cfm)...and my stock radiator could barely keep up with the heat that my little 327 was producing. I saw a huge difference when I re-installed the flex-o-lite fan.