On February 10, 2007, about 2115 eastern standard time, a Piper PA-32-300, N4258R, piloted by a private pilot, sustained substantial damage during a forced landing following a loss of engine power during cruise flight. The 14 CFR Part 91 personal flight was operating in instrument meteorological conditions and was on an instrument flight rules (IFR) flight plan. The pilot and one passenger received serious injuries and two passengers received minor injuries. The flight originated from the Houghton County Memorial Airport, Hancock, Michigan, about 2000, and was en route to the Oakland County International Airport, Pontiac, Michigan. During the flight, the pilot was in communication with the Minneapolis Air Route Traffic Control Center (ARTCC) for the IFR flight. The pilot informed the ARTCC controller that he had experienced a catastrophic engine failure. The pilot attempted to divert to the Pellston Regional Airport, near Pellston, Michigan. The airplane subsequently impacted trees in a wooded area near Pellston. Initial examination of the airplane's engine revealed that the upper portion of the number 4 cylinder barrel had separated from the lower portion. The separation occurred about one inch below the cylinder head. Examination of the separated cylinder by the National Transportation Safety Board's Materials Laboratory revealed that the fracture surface contained features consistent with fatigue. The report further indicates that the origin of these fatigue features emanated from a step in the fracture surface and progressed circumferentially from this point. The fatigue features were present approximately one-fourth of the circumference of the cylinder. Further examination revealed that the origin of the fatigue region coincided with an area near the base of one of the cooling fins that appeared to have been thinned by corrosion. This area was found to have been covered by gray paint. Examination of the airplane's maintenance records revealed that it had accumulated a total of 5,798 hours as of its last annual inspection on November 28, 2006. The engine had accumulated 266 hours since overhaul as of the date of that inspection. The engine logbook indicates that the engine underwent a differential compression test at that time and the compression readings were 76/80 psi, 77/80 psi, 74/80 psi, 74/80 psi, 72/80 psi, and 73/80 psi for cylinders number 1 through 6 respectively. The records indicate that the most recent engine overhaul was completed on May 28, 2000, and all 6 cylinders and pistons were replaced during the overhaul.