A fair question but one which I thought I'd covered in my first post. I wanted to find out for myself what happens if an ABC is "abused" in this way rather than just following the sheep. I'm not exactly unfamiliar with engines so the hot and lean, rev the guts method of breaking in never seemed right to me (as in being the ONLY way to do it). Nor did the oh so familiar cry that even a short rich run on a new ABC would cause irreparable damage. I like to experiment within the limits of what I think is safe. I won't experiment with using 10% oil but I will (and have) experimented with adding water to fuel to find the limits.

So I'm simply experimenting to find out something for myself, I don't expect anyone to change their own methods of running in an ABC. As for whether my particular engine is "loose" or not...define "loose". That comment prompted me to check something a little more accurately though. I mounted a degree wheel in front of the prop and with the plug out I turned the prop until I could feel the piston bind in the taper. It bound up at 45 degrees BTDC (and this is after 18 minutes of sloppy rich running) so this is one thing I'll continue to check after further runs because it'll be a very good indication of whether or not the piston is wearing excessively.

Jim, I've got no idea what a Bluebird N.S. 51 is except it looks like this