PRECAUTIONARY LNDG ON HIGHWAY WHEN ENG RUNS ROUGH.

Narrative

THE PROBLEM AROSE WHILE ENRTE TO A SPRAY AREA. WHICH I AND A STATE OF WI; OBSERVER WERE ENGAGED AS AN AERIAL CHASE PLANE. JUST SW OF KEWAUNEE I NOTICED THE ENG BEGAN TO RUN VERY ROUGH. AFTER CHKING THE EMER PROCS FOR ROUGHNESS OF AN ENG I TRIED PWRING THE ENG BACK TO A LOWER RPM. THE ENG RAN SMOOTHLY AT 1700 RPM. NOT WANTING TO RUIN THE ENG TOTALLY OR CHANCING A TOTAL FAILURE IN A WORSE POS I DECIDED TO LAND THE ACFT. ONE OF THE SPRAY PLTS SUGGESTED A LNDG ON ANY OF THE EW RUNNING ROADS. THIS IS WHAT I OPTED FOR TAKING PRECAUTION OF TFC ON THE HIGHWAY OF CHOICE. AFTER LNDG ON HIGHWAY 29; 3 MI SW OF KEWAUNEE I TAXIED INTO A FARMERS DRIVEWAY AND SHUT DOWN. DURING THE ENTIRE TIME I HAD OIL PRESSURE ON THE ENG AND AFTER LNDG STILL HAD 5 QUARTS IN THE SUMP AND FOUND A BENT PUSHROD FOR THE VALVE THAT FROZE CAUSING THE ROUGHNESS. I FEEL THAT I TOOK THE PROPER ACTION AND MADE A GOOD DECISION; THAT BEING LNDG WHILE STILL HAVING PARTIAL PWR INSTEAD OF THE POSSIBILITY OF THE ENG SEIZING AND NOT HAVING ANY CHOICE ON LNDG.