Based on experience with C177 Cardinals this could point to advanced ignition timing or problems with cooling airflow due poor refitting of engine baffles.
Temps of 440f are a bit high maybe inside the max limit. but I would consider grounding the aircraft at these temps and sorting it out.
Is there a full engine monitor fitted this would give a clue.
Advanced ignition normally shows as higher cylinder head temps but lower EGT. Detonation looks similar.
Baffling is just higher cyl temps but normal EGT.
I have found running with high temps over time can anneal the oil control ring which relies on spring pressure to seal
with no spring pressure the ring leaks oil into the cylinder, causing oil detonation also it can roll over and break damaging the bore.
If no engine work on the annual then go for the baffles if engine work have the mag timing checked or could be both.
Cessna did not do a good job of cooling on the Cardinal as the 210 is the big brother maybe similar problems.
On the Lycoming 360 any cyl temp over 380f is not good and over 400f eating into reliability with possibility of shock cooling problems.
Hope this helps Brian