My open question is the temperature distribution. In a normal operation you will never have al constant temperature on all areas of the piston and sleeve.
The piston and sleeve are hotter on the exhaust side and on top of the piston.
I'm an engine developer for 1:1 diesel engines and our pistons are tapered in axial direction and oval in radial direction, to compensate the different temperatures. Nitro engines are produced with a pinch. During break in, the piston gets it's final geometry. If you run that process with a different temerature distribution to normal operation, the piston may get a "wrong" geometry.

Why do you think the engines are designed with a pinch? I think if there would be a constant temerature during operation, it would be easy to calculate the thermal expansion of piston and sleeve and produce the piston and sleeve with tight tolerances and no break in would be required at all.


My personal expectation is, that a well done classical break in will result in better performance than the break in dutch method.