On June 22, 2002, about 1200 eastern daylight time, a homebuilt Glasair II-SRG, N676EC, was substantially damaged during a forced landing to a clearing in Mill Hall, Pennsylvania. The certificated private pilot/owner/builder was not injured and the passenger sustained minor injuries. Visual meteorological conditions prevailed, and no flight plan was filed for the flight that originated at William T. Piper Memorial Airport (LHV), Lock Haven, Pennsylvania, about 1150. The personal flight was conducted under 14 CFR Part 91. According to the pilot, while the airplane was climbing through an altitude of 2,500 feet, the engine began to miss, vibrate severely, and backfire. When the pilot turned back toward Lock Haven, the oil temperature started to rise, and he was unable to maintain altitude. The pilot turned the magneto switch from the both position to the left position. When the left magneto was selected, engine roughness increased significantly. The pilot performed a forced landing to clearing and impacted trees. A Federal Aviation Administration (FAA) inspector and representative of the engine manufacturer examined the airplane and engine. According to the engine representative, the wiring harness that attached to the back of the left magneto was found partially separated. Two of the four attachment screws were missing, and the other two screws were loose. Additionally, one of the engine's intake clamps was loose. Engine continuity was partially established by manual rotation of the propeller, because the engine could not be turned more than 360 degrees. The engine was examined at Textron Lycoming's teardown facility in Williamsport, Pennsylvania, under Safety Board supervision. Examination of the engine revealed that the crankshaft was fractured through the #3 main bearing journal. A crack was observed from the primary fracture surface through the lightening hole. Fluorescent magnetic particle inspection of the crankshaft revealed over 50 axial cracks in the #3 main bearing journal primarily in two rows. Metallographic cross sections were prepared from three of the cracks. Examination of the cross sections revealed that each exhibited rehardening, rehardening and slight tempering, and tempering of varying depths of up to .06 inches along the entire section of the journal, consistent with a lack of lubrication. Numerous surface cracks were also observed along the journal surface. The engine examination also revealed that the connecting rod bolts were too long for the make and model engine. The engine was last overhauled in 1993, at a total time of 3,260 hours, at which time, the crankshaft was replaced. At the time of the accident, the engine had accrued 318 hours since being overhauled. According to the pilot, there were no maintenance logbooks for the engine, and he did not know the service history of the crankshaft. The pilot purchased the engine in 1993 from the individual who performed the overhaul. The engine sat in the pilot's garage until he installed it on the airplane in 1997. The pilot stated that he preserved the engine with oil, but could not recall what type of oil. He also said that he had never run the engine without oil. The pilot reported a total of 549 flight hours, of which, 351 hours were in make and model. Weather at Williamsport Regional Airport, Williamsport, Pennsylvania, at 1154, included wind from 260 degrees at 7 knots, visibility 6 statute miles, haze and clear skies.