I realize this is an old post but thought I would add to it In 1958 Chevrolet issued a "RED" memo warning not to rev the 348 with three dueces while sitting still for fear of a fan blade exploding. Since then I have seen two case of stove bolts launching fan blades thru the hood, both with no modifications. So it has been my practice to never stand in line with the fan when running an engine. Hope this keeps someone from getting hurt.
