Originally Posted by wizepilot

If you have that many hours in the 421, then you would know it's manifold pressure you are changing (reduction), not RPM. Props generally stay set somewhere from 1700-1900 RPM all the time. Only time you would increase RPM (albeit temporarily) would be if you were flying high, very cold, for a long time. You have to exercise the hubs on the props with warm oil occasionally so they will respond when necessary.