Back in my early 20s, I had a '67 Chevelle which I changed the motor on numerous times. One of my most memorable motors was an all black and chrome high performance small block. After adjusting the valves, I took it out to the highway for a road test. After 10 seconds, smoke started pouring out from under the hood, making it look like a car from a James Bond movie. I limped the car home, opened the hood, and oil had soaked the entire engine bay. After washing the motor down and topping off the oil, I started it to find the leak. Goosing the gas repeatedly, no oil was seen. It was odd due to how much was under the engine bay but, I just could not find the source of the leak. So once again, I took it out onto the highway and sure enough, the smoke comes pouring out again. I pulled over and yep, oil all over the engine bay again.
I dragged it back home, cleaned it again and ran it for over an hour and still, not a drop leaked from anywhere. So being the glutton for punishment that I am, once again I took it onto the highway where yep, you guessed it...smoke started billowing out from under the hood.
Being as frustrated as I was, I elected to pull the motor (thankfully, the engine removal on that car was less than a couple hours of work due to the amount of room underhood), and as the engine is just about to clear the radiator support, there it was (or in this case was not). The bolt that should have been in the fuel pump rod hole was missing! I could see the shaft clear as day. Apparently, revving the engine did not allow enough oil to pass through, but at higher RPMs and under load, the oil would pour out. Having painted the block black definitely did not help in diagnosing the issue either.
Needless to say, I found the correct bolt to take up residence in the hole, dropped the engine back in and happily motored on until it was time for a more powerful motor a couple years later. I made sure that one definitely had the fuel pump bolt in place...and was not painted black.
Anthony in New Jersey