Cylinder Replacement Gone Bad - Grumman Style: Annual on airplane was signed off with a compression check needed 10 later since it was at 68/80 leaking past exhaust. Second check after 12 hours was 50/80 leaking past rings or intake. Pulled cylinder to change and discovered broken top compression ring, and discovered spalled cam lobes and spalled cam followers (tappets). Time for a engine overhaul.