BOTH PILOTS INDICATED THAT WHILE ENROUTE THEY PERFORMED A SERIES OF CHANDELLES AND LAZY EIGHTS. AFTER THE MANEUVERS WERE COMPLETED AND THE FLIGHT WAS AGAIN ON COURSE FOR MODESTO, THE ENGINE REPORTEDLY 'SPUTTERED' SUDDENLY, THEN QUIT COMPLETELY. ENGINE POWER COULD NOT BE RESTORED AND THE AIRCRAFT COLLIDED WITH TREES AND TERRAIN WHILE ATTEMPTING AN EMERGENCY LANDING IN A MOUNTAINOUS AREA AT DUSK. ALL FUEL LINES WERE FOUND TO BE INTACT AND PROPERLY SECURED TO THEIR RESPECTIVE COMPONENT FITTINGS. APPROXIMATELY 16 GALLONS OF FUEL WAS FOUND IN THE FUEL TANKS. THE AIRCRAFT WAS EXAMINED BY FAA AIRWORTHINESS INSPECTORS AND NO SYSTEM OR ACCESSORY ABNORMALITY WAS FOUND. THE CLOSEST OFFICIAL WEATHER REPORTING STATION WAS REPORTING A TEMPERATURE AND DEW POINT OF 59 AND 50 DEGREES RESPECTIVELY. THE CARBURETOR ICING PROBABILITY CHART NOTES THAT THE TEMPERATURE AND DEW POINT FALL INTO AN AREA DEFINED IN THE CHART AS 'SERIOUS ICING --CRUISE OR CLIMB POWER'.