AFTER TAKING OFF AT HEBER CITY, UT, THE PLT TURNED TO A 090 DEG HEADING & BEGAN A CLIMB WITH FULL THROTTLE, MIXTURE FULL RICH, 80 TO 90 KIAS & APRX 500 FPM RATE OF CLIMB. AT APRX 6500 FT MSL, HE ALTERED THE COURSE TO 110 TO 115 DEG TO PROVIDE BETTER TERRAIN CLEARANCE, OVER A SLIGHT VALLEY FORMED BY CREEK DRAINAGE. AT THAT POINT, THE CLEARANCE WAS REPORTEDLY ABOUT 1000 FT. AS THE CLIMB CONTINUED, THE PLT NOTICED THAT THE TERRAIN WAS GRADUALLY GETTING CLOSER. AS HE NEARED THE TOP, HE SUDDENLY REALIZED THAT THE ACFT MIGHT NOT BE ABLE TO MAKE IT OVER. A 180 DEG TURN WAS STARTED. HOWEVER, AS A LEFT BANK WAS ESTABLISHED FOR THE TURN, THE ACFT FELT MUSHY & STARTED TO LOSE ALT RAPIDLY. THE PLT ROLLED THE WINGS LEVEL & PULLED BACK ON THE YOKE WHEN GROUND CONTACT WAS POSSIBLE. HOWEVER, THE DESCENT CONTINUED & THE ACFT CRASHED ON A TREELESS, SNOW CVRD SLOPE AT 9300 FT. THE PLT SUGGESTED CARBON MONOXIDE MIGHT EXPLAIN HIS INDECISIVENESS, BUT AN EXAM OF THE ENG & EXHAUST SYS REVEALED NO PREIMPACT MALFUNCTION OR FAILURE.