Originally Posted by stefan

Ok, here is what has been working for me:

I heat the entire engine up with a heat blower untiil it has at least 80-90°C (the entire engine, not just the head) before I ever start it up.

Start the engine and put it on the track immediately and drive the car at a good pace keeping temp up to 100°C. I do not adjust the needle towards rich, I actually want the car to shift into second gear.

Cool down to ambient temperature and run another tank the same way and that's it.

Since the microcast pistons are not as tight as the machined pistons, this is all they need, the entire break in is actually more for the bearings and conrod.

The more those engines are run under "break in conditions" (rich and cool), the more the microcast piston is wearing out before she ever makes power.

This has been working for me. It feels strange to do this the first times, but the benefits are great.