Well.

I've done 'em both ways. A tank on the ground, then fly slightly rich. Full power won't be available the first few flights/tanks. Run a few tanks on the ground in a stand to get familiar with the engine. Full power won't be available for the first few tanks. They both work.

We used to use break in newly overhauled radials in a test cell with an unusual prop/club that had 4 very short/stout blades with steep pitch.

Terry in LP