RV-6 general aviation pilot reported an engine malfunction during cruise. The pilot diverted to a non-towered alternate airport and landed safely.

Narrative

Planned VFR flight from ZZZ to ZZZ1 at 6500 feet. Weather conditions forecasted to be VFR for entire route of flight. Start/taxi/take-off uneventful. Departed VFR from ZZZ at approximately XA:45. Picked up VFR flight following with ZZZ Departure shortly after take-off. The climb to 6500 feet was uneventful. At approximately XB24; the engine monitoring system indicated rapidly decreasing exhaust gas temperature from cylinder 4; followed by slowly decreasing cylinder head temperature for cylinder 4. A small vibration sound was noticed. At the time I was in radar and radio contact with Center. I decided to discontinue my flight to ZZZ1 and divert to ZZZ2. I tried to communicate intentions to Center twice without any reply. I then proceeded direct to ZZZ2 in the blind on Center frequency. I switched to ZZZ2 Unicom frequency and declared my intention to land straight in to runway XX. There was no other traffic in the pattern. Landing and taxi to ramp was uneventful. After landing I made a call in the blind reporting safely landing at ZZZ2. After shutdown; I phoned Center and reported safely landing at ZZZ2. Controller expressed his thanks for reporting. No FAR's were violated during this sequence of events. An airframe & propulsion mechanic determined that a cracked exhaust pipe was the cause of the temperature anomalies and the vibration noticed. No parts came off the aircraft.