THE ACFT COLLIDED WITH TREES WHILE MANUEVERING IN MOUNTAINOUS TERRAIN. THE PLT HAD PLANNED A LOCAL FLIGHT FROM HONOLULU TO MAUI AND RETURN. ONCE OVER THE ISLAND OF MAUI, THE PLT NOTIFIED THE FSS THAT HE WAS CHANGING HIS ROUTE AND WOULD BE PASSING THROUGH THE ISLAND'S CENTRAL VALLEY FROM N TO S. AFTER TALKING TO THE FSS HE DECIDED TO OVERFLY A 10,000 FT MOUNTAIN TO SHORTEN HIS ROUTE. AS HE APPROACHED THE MOUNTAIN HE REALIZED THE TERRAIN WAS RISING FASTER THAN THE ACFT'S CLIMB. THE PLT TURNED LEFT TO AVOID A COLLISION WITH THE TERRAIN AND THE ACFT LANDING GEAR STRUCK A TREE AT THE 4,500 FT LEVEL. THE ACFT AIRSPEED WAS APRX 55 KTS WHILE IN A 15 TO 20 BANK. THE PLT ELECTED TO LAND IN THE TREES. THE ACFT SYSTEMS WERE EXAMINED AND THE FOLLOWING DEFICIENCIES WERE NOTED; THE NO. 3 LEAD ON THE LEFT HAND MAGNETO WAS CUT, THE CAMSHAFT LOBES WERE EXTREMELY WORN, AND ALL LIFTER FACES EXTREMELY PITTED.