APPROXIMATELY 30 MIN AFTER DEPARTURE THE ACFT RETURNED TO THE ARPT TRAILING SMOKE & OCCASSIONAL FLAME FROM AN AREA NEAR THE COWL FLAPS & NOSE GEAR DOORS. THE PLT DID NOT MAKE A STRAIGHT IN APPROACH BUT APPEARED TO BE IN A NORMAL TRAFFIC PATTERN. THE ACFT STALLED WHERE A LEFT BASE LEG TURN WOULD HAVE BEEN MADE. THERE WAS EVIDENCE OF HEAT & SMOKE IN THE COCKPIT. INSIDE PORTIONS OF THE BROKEN WINDSHIELD WERE SOOTED. THE UNDERSIDE OF THE EMPENNAGE WAS COVERED WITH FRESH OIL OVER ITS ENTIRE LENGTH. OIL STAINS & FRESH OIL LEAKAGE SIGNATURES WERE PRESENT ON THE OIL DRAIN HOUSING ATTACHED TO THEACCESSORY CASE. THE REAR CLAMP WAS LOOSE ON THE P/N 24827 HOSE WHICHCOUPLES THIS HOUSING TO THE INTAKE & OIL DRAIN MANIFOLD. THE ACFT WAS EXTENSIVELY MODIFIED BY THE OWNER BETWEEN 10/79 & THE DATE OF THE ACCIDENT. NO FAA FORM 337 (MAJOR REPAIR & ALTERATION) HAD BEEN FILED SINCE 5/14/75 EVEN THOUGH A LARGE ENGINE & NUMEROUS MODIFICATIONS TO THE ACFT HAD BEEN ACCOMPLISHED BY THE OWNER.