Engine parts? Lessee, the crankcase in the main center part of the engine, to which the cylinders attach. The bulbous affair on the front of the engine that the prop sticks into is the gearcase, because it houses reduction gearing. The engines usually turn 3000 to 3300 rpm, and the prop rpm is reduced to around 2000 on big radials.
The magnetos are box-like affairs, come in pairs, and could be mounted in front of the cylinders or in back, depending on the engine. The R-2800 had them in front. Usually black, they make the spark for the plugs. The plug wires are usually routed through a conduit around the crankcase, and exit at each cylinder, run up along a pushrod tube to one plug on the front of the cylinder and another wire to a plug on the back.
At the top of each cylinder, where it becomes Y shaped, are oblong bumps that are the rocker box covers, the valve rocker arm is in here, and they constantly leak oil. Heck, the whole engine leaks oil.
If cylinders are painted, it doesn't stay on long, either, the heat flakes it off. Gear and crankcases fare a little better. Hope this helps!