Originally Posted by
swervin'mervin
This is normally pilot induced I believe. They are easy to shock cool decending from altitude without monitoring CHT.
This is true, its often the case with engines like this, The Cessna 421 is a brilliant aircraft but very sensitive in this respect. The trouble from this point of view is that an aircraft offered for rental is probably going to suffer worse than most, therefore you'll end up paying more per hour weather its your mistake or someone elses.