RPTR'S ENG COMMENCED RUNNING ON 3 OF THE 4 CYLINDERS DURING CLBOUT THROUGH 2100 FT. THE RPTR RETURNED FOR LNDG. THE ENG QUIT COMPLETELY ON DOWNWIND.

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ON CLBOUT FROM CHINO. TKOF ON RWY 21 (INTXN). UPON REACHING 2100 FT MSL; ENG BEGAN RUNNING ROUGH (AS IF ON 3 OF 4 CYLINDERS). NOTIFIED TWR INTENTION TO RETURN TO LAND WITH ROUGH ENG. USED CARB HEAT WITH NO SIGNIFICANT CHANGE. DECIDED NOT TO USE MAGNETO SWITCH DUE TO LOW ALT AND POTENTIAL ENG STOPPAGE WITHOUT ABILITY TO DO IN-AIR RESTART (ACFT NOT STARTER EQUIPPED). TWR NOTIFIED ME SMOKE OBSERVED UNDER ACFT WHILE 1 MI OUT. DECLARED INTENTION TO SHUT OFF ENG ON DOWNWIND (MY REASON WAS SOURCE OF SMOKE COULD BE OR CAUSE A FIRE WITH DISASTROUS RESULTS IN A FABRIC COVERED ACFT). UPON REACHING DOWNWIND I MADE FIRST PWR ADJUSTMENT SINCE OCCURRENCE BY SLOWLY REDUCING PWR. AT ABOUT 40 PERCENT SETTING; ENG STOPPED. CHINO TWR CLRED ME TO LAND AND I DID A NORMAL DEAD STICK LNDG. AFTER LNDG AND ROLLING OFF RWY; FOUND THAT PROP MOVED STIFFLY AND ROTATION BLOCKED AFTER 90 DEG ROTATION BACKWARD. ENG DISASSEMBLY IN PROGRESS. CHINO TWR AND GND MAINT WERE GREAT. CALLED AND THANKED INSTRUCTOR FOR GREAT TRAINING 4 YRS AGO. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THE RPTR STATED HE WAS FLYING AN AERONCA CHAMP 7 ACFT WITH A 75 HORSEPWR ENG. HE SAID THE ENG WAS FOUND TO HAVE SWALLOWED A VALVE. THE STEM HAD BROKEN JUST BELOW THE VALVE SEAT AND THE HEAD CAME OFF AND POKED A HOLE IN THE PISTON. THE ENG HAD JUST COMPLETED A MAJOR OVERHAUL 35 HRS AGO BUT THE VALVES HAD NOT BEEN REPLACED. THERE IS ABOUT 45 HRS NOW ON THE NEW OVERHAUL. THE ENG RUNS FINE. THE VALVES WERE ALL REPLACED. THE ONLY THING HE WOULD HAVE DONE DIFFERENTLY WOULD HAVE BEEN TO HAVE REFERRED TO THE EMER CHKLIST. HE DID COVER EVERYTHING ON THE CHKLIST BUT THOUGHT IT WOULD BE GOOD TO SAY HE HAD CONSULTED THE CHKLIST. WHEN THE ENG QUIT IN THE TFC PATTERN THE PROP ACTUALLY STOPPED. THE ENG FROZE. THE FAA DID NOT GET INVOLVED IN THE EVENT. HE NEVER DID HAVE TO MAINTAIN ALT AFTER PWR LOSS. HE DOES NOT BELIEVE HE WOULD HAVE BEEN ABLE TO MAINTAIN ALT ON THE 3 OF 4 CYLINDERS THAT WERE RUNNING. HE BELIEVES SINCE THE WINDS WERE ALMOST NIL HE WOULD HAVE LANDED ON THE RWY 03 OPPOSITE OF RWY 21 HE TOOK OFF OF IF THE ENG HAD QUIT COMPLETELY WHILE AT 2100 FT MSL. CHINO ELEVATION IS 650 FT.