Engine block. Moving parts of the engine are mounted in it. Various devices are attached to the block, such as: alternator, starter and elements of the ignition system.
Head. Closes the cylinder space from above. There are air supply channels in the head, exhaust fumes, engine coolant flow channels, valve seats, bearings and guides of the valve control mechanism, sockets for screwing in spark plugs and combustion chamber. The gasket between the cylinder head and engine block prevents false air and coolant from entering the cylinder.
Cylinder. The cylinders together with the head determine the engine's displacement. The inner walls of the cylinders are carefully ground (honed) to the right size, depending on the diameter of the piston. A liquid is used to cool the cylinder walls, flowing through channels in the engine block and oil sprayed onto the plaster.
Piston. It takes the energy released in the combustion process and transfers it to the crankshaft via the connecting rod. The piston consists of a crown, grooves with piston rings in them, piston pin and skirt hubs. Two upper sealing rings prevent combustion chamber gases from entering the crankcase. The lower scraper ring collects excess oil from the cylinder walls and drains it to the oil pan.
Connecting rod. It connects the piston to the crankshaft. It consists of a head (in which the piston pin rotates), connecting rod head cap and cap (in which the crank pin rotates).
Crankshaft. Converts the reciprocating motion of the pistons into a rotary motion. It consists of main tenons (bearings in the crankcase), crank pins (for attached connecting rods) and from the arms of the cranks (connect main journals to crank pins).
Valves. The intake valves let fresh air or mixture into the cylinder, and the exhaust gas discharge to the exhaust system. Golf engines have one to three intake valves and one or two exhaust valves per cylinder. All parts involved in opening and closing the valves are components of the timing system.
Camshaft. It opens and closes valves at the right moment. Each valve is controlled by a shaft cam via hydraulic tappets or valve levers. The camshaft is driven by a toothed belt from the crankshaft, or from the second camshaft.
Diesel used in VW Golf 4 is an OHC engine (Over Head Camshaft), that is, an overhead valve engine. Its camshaft is mounted in five places and driven by a toothed belt from the crankshaft.