The photos shows the crap on top of the pistons, when turning the engine over by hand to ensure the cam timing was correct following the timing belt change procedure, oily, greasy, gritty crap fell from the combustion face of the cylinder heads down into the cylinders, it piled up so high that the engine would not fully rotate. I have to pull the heads to get the crap out of there. After cleaning and re-surfacing and installing the heads the engine rotated just fine.