I'm not sure it's quite that simple (for one thing, no two engines are ever identical) because everyone seems to think that pinch is the be all and end all of the condition of the engine. In my infamous experiment where I flogged a new ABC slobbering rich for 45 minutes the pinch didn't change from what it was straight out of the box. A further 20 minutes of running closer to what's suggested in post #1 and the pinch had all but disappeared. My conclusion from this was that very rich running does nothing whatsoever as far as running in the piston/liner although the rod was running in very nicely.

Note that these are only my conclusions from my hands on experiment with my own engine and, although I know for myself what procedure to use in future (which I've since done several times), I'll leave it up to the individual to decide for themselves how they want to go about it. Hmmmm...this suggests a new thread on a somewhat related topic .