1987 Plymouth Colt 1.5 Liter mileage: 134,000. We were on a trip when the valves started knocking really loud. We pulled over immediately and shut it down, and added some oil, when I tried to restart it; it ran for about five seconds then died. I removed the valve cover, rocker arms and timing belt, camshaft turns smoothly. The crankshaft will turn easily about 3/4 turn then locks tight. The car has never burned or leaked oil, but the oil light stays on. I checked the oil regularly and used synthetic, thinking it would prolong the car's life. I am thinking a broken connecting rod, but I'm a carpenter not a mechanic. Any advice?