An interesting PM from an old mate who has been flying Chieftains relatively recently...and for
a smarter than average operation/CP.
My Chieftain manual does not appear to state any particular limit but.....
When I was doing casual work for XXXXX, company policy stated that the engines could be run flat out, ie full throttle and 2575rpm BUT at full rich mixture!!!!
Also; leaning in the climb (40''MAP 2400rpm) was streng verboten!!
Others have already covered this which is why I have'nt posted to this effect.