On July 15, 2021, about 0850 Pacific daylight time, an experimental amateur built RV6A, N468AC, was substantially damaged when it was involved in an accident near Riverside Municipal Airport (RAL), Riverside, California. The flight instructor sustained a serious injury, and the pilot sustained a minor injury. The airplane was operated as a Title 14 Code of Federal Regulations Part 91 personal flight. The pilot stated that the purpose of the flight was to conduct an airplane checkout and flight review. During a power-on stall, the engine stopped; the pilot stated that he immediately switched fuel tanks, and the engine restarted. The pilot suggested that the airplane return to RAL, and the flight instructor told him to obtain a landing clearance. The flight instructor assumed control of the airplane because the pilot had not landed the airplane before. The tower controller instructed the pilots to extend the downwind leg for landing traffic. While on final approach to land on runway 27, the engine stopped again. According to the pilot, the flight instructor thought that the airplane was not going to reach the runway. The airplane subsequently impacted terrain short of the runway and came to rest inverted on a northern heading 450 ft from the threshold of the runway. Postaccident examination of the airplane found a blue liquid, consistent with 100 low-lead fuel, draining from the lower cowling near the quick drain. About 6-7 gallons of fuel were drained from the left fuel tank, and about 16-17 gallons of fuel was drained from the right fuel tank. The engine was started and ran uneventfully for several minutes at various power settings, including full power. No evidence of any pre existing mechanical malfunction or failure was revealed that would have precluded normal operation of the engine.