North american T6 pilot reported diverting to a nearby airport when his engine began running rough.

Attributes
ACN	1303326
Time
Date	201510
Local Time Of Day	1801-2400
Place
Locale Reference	ZZZ.ARTCC
State Reference	US
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Make Model Name	Texan T6/Harvard (Antique)
Operating Under FAR Part	Part 91
Flight Phase	Cruise
Flight Plan	VFR
Component
Aircraft Component	Engine
Person 1
Function	Pilot Flying Single Pilot
Qualification	Flight Crew Air Transport Pilot (ATP) Flight Crew Flight Instructor Flight Crew Instrument Flight Crew Multiengine
Experience	Flight Crew Last 90 Days 100 Flight Crew Total 6000 Flight Crew Type 85
Events
Anomaly	ATC Issue All Types Aircraft Equipment Problem Critical Ground Incursion Runway

Narrative:

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.

Original NASA ASRS Text

Title: North American T6 pilot reported diverting to a nearby airport when his engine began running rough.

Narrative: 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.

Data retrieved from NASA's ASRS site and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.