C172 ENG QUIT DURING PWR-OFF STALL PRACTICE RESULTING IN AN ACTUAL OFF ARPT FORCED LNDG. NO INJURIES OF ACFT DAMAGE.

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AT APPROX XA00Z ON FEB/XA/00; I EXPERIENCED COMPLETE LOSS OF ENG PWR WHILE GIVING DUAL INSTRUCTION IN A C172. WE WERE AT 4500 FT MSL (APPROX 3000 FT AGL) OVER A RESERVOIR IN A PWR-OFF STALL WITH CARB HEAT APPLIED. I IMMEDIATELY TOOK THE CTLS FROM MY STUDENT; ESTABLISHED VG/BEST GLIDE FOR THE ACFT; TROUBLESHOT; CONTACTED 121.5; SQUAWKED 7700; AND GLIDED IN THE DIRECTION OF A GRAVEL STRIP. THE ACFT NEVER REGAINED PWR. THIS WAS MY SECOND DAY AS A FLT INSTRUCTOR. IRONICALLY; THE PREVIOUS DAY; I HAD SIMULATED AN ENG FAILURE WITH ANOTHER STUDENT OVER THE SAME RESERVOIR TO THE VICINITY OF THE GRAVEL STRIP. WE CAME IN AT LEAST 1500 FT HIGH OF THE STRIP. I ELECTED TO EXECUTE A 360 DEG TURN FOR SPACING. ON FINAL APCH; BOTH MY STUDENT AND I DETERMINED THAT WE WOULD GLIDE SHORT OF THE STRIP AND LANDED WITHOUT DIFFICULTY ON A CLOSER FIELD. MY STUDENT AND I SUFFERED NO INJURIES AND THE PLANE WAS NOT DAMAGED. THE ACFT WAS LATER PULLED FROM THE FIELD TO THE STRIP AND FLOWN BACK TO ITS HOME ARPT AFTER AN INSPECTION BY AN AUTH A&P MECH WHO DETERMINED THE CAUSE TO BE CARB ICING. MY PRIOR FLT EXPERIENCE IN C172'S HAD BEEN IN ACFT WITH LYCOMING ENGS. THE ACFT I WAS FLYING THAT DAY HAD A CONTINENTAL ENG. A MECH AT THE ARPT INFORMED ME THAT CONTINENTAL ENGS ARE MORE SUSCEPTIBLE TO CARB ICING THAN LYCOMING'S BECAUSE A LYCOMING'S CARB IS EXTERNALLY ASSISTED BY THE WARMTH OF THE NEARBY OIL SUMP. ALTHOUGH I WAS OPERATING THE ACFT IN A MANNER CONSISTENT WITH MY TRAINING; THE EXPERIENCE PROVED INVALUABLE TO MYSELF; MY STUDENTS (PRESENT AND FUTURE); AND ALL OF THE PLTS WITH WHOM I HAVE CONTACT AS THEY MAY SOMEDAY ENCOUNTER SIMILAR SITS WITH CONTINENTAL-EQUIPPED AIRPLANES.