Originally Posted by
gmwillys
The rotating assembly would be the crank shaft, connecting rods, pistons, and the valve train. Some machine shops will assemble everything to ensure proper fit, then others fit everything, and leave the parts out for the owner to assemble.
The starter can turn alright without a load, but if there is a short in the windings, or the brushes are shot, the starter will not have enough umph to get the engine turning. Have it checked out by a starter rebuild shop, to at least have it checked.
Also check the condition of the battery cables. You can check the resistance of the cables, to see if it is high. If so, the voltage drop can cause the starter to act up.