The Federal Aviation Administration (FAA) aviation safety inspector reported that, during a telephone conversation, the pilot reported that, during the climb, he noticed the engine cylinder heat temperature gauge exceed 500°F. The pilot added that he immediately turned back to the departure airport, and while in the downwind for the landing runway, the engine lost power. The pilot further added that the airplane immediately lost altitude and cleared a tree line in the path to the runway but then impacted terrain hard in a base-to-final flightpath near the runway threshold. He added that, when he exited the airplane, he observed an engine cowl plug installed on the right side of the engine cowl and removed it. The right wing and fuselage sustained substantial damage. The FAA inspector reported that he traveled to the accident, and while on-site, he observed the left cowl plug melted onto the engine cylinders. He added that the right cowl plug was found on the ground near the airplane. The pilot reported that there were no preaccident mechanical malfunctions or failures with the airplane that would have precluded normal operation. The pilot did not submit the National Transportation Safety Board Form 6120.1 Pilot/Operator Aircraft Accident/Incident Report.