RE: How important is the break in procedure?
Hugh,
So, also according to your words, heat treatment does not acutally take place during the break-in of a glow engine.
With the exception of the meehanite-steel engines' piston, no size-stablization happens either.
So, in any AB(X) engine, the only objective of the break-in is to achieve optimal part-mating, through mutual polishing...
Maybe the cast-iron ring (in engines with ringed pistons) also needs size stabilization, through heat-cycling; and also optimal part-mating, through mutual polishing.