Texan T6/Harvard (Antique)
Flight Crew Air Transport Pilot (ATP); Flight Crew Flight Instructor; Flight Crew Instrument; Flight Crew Multiengine
Flight Crew Last 90 Days 100; Flight Crew Total 6000; Flight Crew Type 85
ATC Issue All Types; Aircraft Equipment Problem Critical; Ground Incursion Runway
Flight Crew Landed in Emergency Condition; Flight Crew Landed As Precaution; Flight Crew Diverted
Aircraft
While flying at 1;500 ft MSL I experienced an engine malfunction where the engine rapidly began running rough and there was a significant loss of power.  It appeared that one of the 9 cylinders had malfunctioned.  I began a climb and pointed at the closest runway and [contacted] Center.  While in the climb to approximately 2;500 ft it appeared that both runways were closed however XYR had men and equipment on it.  I questioned Center as to what runway was open and they advised me to squawk a code and I advised I was unable to squawk at that time and that it was an emergency situation and I was landing.  I then landed the aircraft uneventfully with the engine still running.
North American T6 pilot reported diverting to a nearby airport when his engine began running rough.