On July 16, 2011, at 1830 Pacific daylight time, a Piper PA-24-250, N5532P, experienced a loss of engine power during cruise flight. The pilot subsequently made a forced landing to a private grass strip near Lopez, Washington. The owner/pilot operated the airplane under the provisions of 14 Code of Federal Regulations Part 91 as a personal cross-country flight. The commercial pilot, the sole occupant, was not injured. During the landing roll, the left wing was substantially damaged when it struck a fence post. Visual meteorological conditions prevailed for the flight that departed Roche Harbor Airport (WA09), Roche Harbor, Washington, at 1815. The flight was destined for Frontier Airpark (WN53), Lake Stevens, Washington. No flight plan had been filed.The pilot reported that the airplane was in cruise flight about 2,000 feet near Spencer Island. He heard a loud bang, felt an extreme vibration, had smoke in the cockpit, and oil covered the windshield. He reduced engine power to idle, opened the side vent window, and was able to regain visibility. He chose the closest landing strip, and landed the airplane. On the landing rollout, the pilot stated that the grass strip was shorter than what he would need to bring the airplane to a stop and the runway surface was wet. He intentionally placed the airplane in a "ground slide," and prior to coming to a stop, the left wing struck a fence post. During the post-accident inspection of the engine, the pilot observed a crack in the engine block near the rear cylinder on the pilot's side. No further examination was accomplished.