ALTDEV DURING A RETURN LAND EVENT.

Narrative

SHORTLY AFTER TKOF ON AN INST TRAINING FLT INTENDED TO PRACTICE APCHS AT RAL; CNO; AND POC; A STRONG ODOR OF BURNING OIL WAS NOTICED CAUSING GREAT CONCERN TO THE STUDENT A MOMENT LATER; WHILE CLBING THROUGH 3800 FT FOR THE ASSIGNED ALT OF 5000 FT; THE ENG BECAME QUITE ROUGH. CARB HEAT; MIXTURE AND MAGNETOS WERE CHKED WITHOUT HELPFUL RESULTS. WE REQUESTED A RETURN TO BRACKETT NOTIFYING APCH CTL OF OUR PROBLEM BUT NOT DECLARING AN EMER; AS ALL ENG GAUGES WERE NORMAL AND THE SLIGHT PWR LOSS AND SHAKING WERE NOT TOO ALARMING CONSIDERING OUR PROX TO BRACKETT. WE WERE OFFERED EITHER THE ILS APCH OR VECTORS; AND ACCEPTED A VECTOR RETURN. WE WERE DSNDED TO 3000 FT AND VECTORED ALONG THE NORMAL VOR APCH. ABOUT 1/2 MI INSIDE OF GOLDIE (FAF FOR VOR APCH); I ALLOWED THE ACFT TO DSND ABOUT 300 FT BELOW THE ASSIGNED ALT; PROBABLY DUE TO MY EXTREME FAMILIARITY WITH THE VOR APCH AND RECOGNIZING THE TERRAIN WHICH WOULD HAVE PERMITTED 1800 FT AT THAT POS. APCH NOTIFIED ME OF THE LOWER THAN ASSIGNED ALT; AND AS WE HAD BROKEN OUT AND HAD THE ARPT INSIGHT; CLRED ME TO TWR.