Guys. It is very simple to demonstrate how painting something black makes it radiate heat faster. Get yourself one of those laser temp gauge things and try it.

But one thing is a MUST. If you are going to paint a radiator black you must use correct radiator paint. I don't know why but it works much better. I tried it.

In fact because I run a 1970 Challenger it was important to paint the front of my aluminium radiator so it could not be seen from the front through the 1970 grille. So I did. But I left the engine side of it natural aluminium so it looks trick along with the engine. Best of both worlds.