I just went through the same exact thing (zero compression on 2 cylinders, no start) on my 216. It was a combination of stuck valves and tappets out of adjustment. If you have a fouled valve seat it may be giving you a false tappet measurement (i.e. valve not seating appears to be proper lash setting). I pulled my head and valvetrain, polished all the valves and seats, and reassembled with a new head gasket. Be sure to torque the head in the appropriate pattern (basically outward spiral from the center) to the appropriate spec (75-80ft-lbs) or your head gasket won't seal. I only know because I screwed it up the first time.
