AFTER SPENDING THE NIGHT IN TUCSON, ARIZONA, AND REFUELING THE AIRCRAFT TO ITS 36 GALLON CAPACITY, THE PILOT TOOK OFF ON HIS FINAL LEG HOME. HE WAS AT AN ALTITUDE OF 6000 FEET MSL APPROXIMATELY 30 MINUTES AFTER TAKEOFF WHEN THE ENGINE FAILED. HE ATTEMPTED TO MAKE A FORCED LANDING AT PINAL AIRPARK, ARIZONA, LOCATED APPROXIMATELY 31 MILES NORTH-NORTHWEST OF TUCSON, BUT COLLIDED WITH THE ROUGH TERRAIN ABOUT 350 YARDS SHORT OF RUNWAY. ACCORDING TO FAA INSPECTORS NO OBVIOUS FAILURES OR MALFUNCTIONS IN THE ENGINE WERE NOTED DURING THEIR ON SCENE INVESTIGATION.