Lighten up. Nobody said don't paint it. Your question was what was it painted originally, the answer was "nothing".

I paint everything that I put back together because I like the neat appearance. But I am not restoring to "factory new appearance" either.

So if I want to paint the block black, I go ahead and do it. If the valve or cam covers get painted aluminum color, it's because I think it contrasts the black nicely.

And if my newer truck engine is a bright gold color, it's because there were three spray cans in that color in the Clearance section at Walmart!

R.