Some Club members here disassembled a TR4 motor that was running but was down on power and blowing some smoke. They found that the all the top compression rings were broken on all four pistons. The engine was stock except for an M766 performance cam. I don't know how hard the car was driven by the PO but I was wondering if the race cam, without any other modifications to the engine. may have contributed to the broken rings and if so what was going on there that would cause the damage ie. valves misadjusted or timing wrong etc. or not related to cam?