[Christ]

Ok, here's the thing -

People always think that the thermostat doesn't open up until the engine is already up to temp. While this is partially true, it's also partially false.

On a full warm-up cycle, depending on conditions, the thermostat could open 5 times... It could open 10 times... Hell, it could open 35 times.

What actually happens in your coolant system is that the local (near the thermostat) coolant heats up. This causes the stat to open, allowing the water pump to push the coolant through the stat, into the radiator, where it is cooled.

Ok, so the coolant gets cooled by the radiator, right? Right. What happens to the already cold coolant that was in the radiator when the hot coolant displaced it? Oh... it goes back into the engine. Cold coolant hits the thermostat, and it closes, right? So now the engine has to heat the coolant back up to temp, open the thermostat, and allow the pump to push it out into the radiator... So that coolant leaves, and some of the already warmed coolant goes back into the engine... so the stat stays open? Nope.

Remember, the first set of coolant was in the radiator. What does the radiator do again? It cools - that's right. So now, the coolant that was already heated once has just cooled down (here's the good part) a lot. Which means the engine has to heat it back up, to open the stat, to allow it into the radiator, to be cooled, so the already cooled coolant can flow back into the engine, to be heated back up, so on, so forth.

So, you can see that a grille block will help warm-up times in this manner. It will prevent the radiator from cooling the heated coolant so much/so quickly, meaning less heat energy has to be wasted back into it each time there is a thermostat cycle.