My airline pilot friend, who is building a Lionheart, told me what the CHTs were on the P&Ws he flew on the twin-engine Convair. Max CHT, 260C, 500F. METO, 232C, 450F. RECOMMENDED cruise, 204C, 400F. This was the temperature that they were supposed to adjust their cowl flaps to achieve during cruise! BTW, I was asked, on my first posting about CHT, to reference the source of my opinions, which I subsequently did. I hope all that respond with other views will do likewise.

Paul,

 

I have never seen damage done to a piston operated "too cool".  Here is a photo of one operated "too hot". Notice the crown of the piston is eroded away. 

 

Regards,

 

Jeff