For what its worth, from some of my own personal experience (hands on, not 2nd hand) you can indeed wear out prematurely an ABC type engine by breaking it in running too cool (whether it be too rich, too cold outside, at a reduced throttle for too long, etc).

Some engines may be more prone than others - but I would never recommend running a lapped aluminum piston engine "slobbering rich" or at a reduced throttle setting (equally as harmfull) when new, for extended periods of time.


AJC