These 6.2 liter engines are prone to valve spring failure. This engine was no exception. It was presented to us with 1-3 intermittently dead holes, and was basically undrivable. A replacement engine was a bit over budget, so we in housed the repair. A complete rebuild was performed, including crank polishing, main and rod bearings, rings, honing, decking, vavle lap, valve stem seals and valve springs (to name a few). It is currently running and back in service..