Allow the engine to cool between tanks with the piston in the lower position. You want your piston in the lowest position for the following reason for cooling. The top portion of the cylinder is actually tigher than the bottom. As the cylinder cools it will contract therefore you don't want it contracting around the piston at it's tightest spot.
Kabayan,
Paano ko ba ma-sure na yung piston ko eh is in lower position...di ba nasa loob ng engine yun? May way ba para magawa ko yun.
Salamat.