340 Overheat / Radiator Geyser

Video was set to unlisted but I changed it to public. Thanks. Nope...Everything stays where it should when revving the engine. It only exploded out of the radiator when I shut the engine off. I do try to have an open mind, especially since I've had nothing but basically unexplainable issues with this car since almost day 1.
How quickly after you cut the car off did the radiator expel coolant?