Note(!) This model year ('77) does not have the magical four holes that later years have. I wonder whether this means my pucks are in more danger than with the "holy" models. One thing that concerns me in this regard -- with the lever down, with my hand covering the group-head opening, when I pull the lever up I can feel a vacuum on my hand. I can't imagine that's good for a puck. Could any of you folks with holes in your pistons tell me whether this experiment yields a vacuum.