nrp wrote:

Max Conrad (ferried Pipers all over the world in the 40s and 50s) ran
fully leaned & with full carb heat when he was in his max range mode.
Do you know of any reason not to, assuming a low power setting? It
would improve the mixture distribution, something the O-470s are
notoriously poor at. It would also reduce the inlet air density,
allowing things to operate with less pumping loss.

On the 470's, in cruise, you give it whatever carb heat gets you a carb
temp of 40-45F. Running at full carb heat makes no sense whatsoever.