The total runtime of “Heavy Metal Parking Lot” is all of 17 minutes. But the legacy of what happened one evening in Landover has endured for 40 years. Directors John Heyn, 68, and Jeff Krulik, 65, told The Banner they still kind of marvel at what they captured in their documentary short. “We ventured out that day not really knowing what we were gonna get,” Krulik said. “We didn’t know what we were in for.” What they got was a pure distillation of fandom that has been embraced by weirdos for decades.