I have had great luck with a variation of the heat cycle method. I do it for 4-6 minutes at a time. I pre-heat the engine with a heat gun (very important) and I wrap the head in foil. This way I can hold 200-220f at idle and a slightly rich setting to make sure lots of oil is passing through the engine. After 4 cycles like this I start running it very lightly on pavement for a couple more cycles. It is very easy on the engine and makes for a good, tight piston/sleeve fit. The heat gun and the foil are what makes the difference.