[brucepick]

I keep one of my ScanGauge displays set to show engine coolant temp. it reads out in 2ºF increments.

From that I know if the engine is getting more or less cooling than it needs. I've seen this engine stabilizes at 182ºF if all is well. If it's consistently above or below that temp I know the amount of air going through is too little or too much.

That temp is just my engine; I'm not saying that's the magic temperature for all. I'm saying you really can see how your grill block and cooling system are doing if you observe the temperatures.