The crankshaft of all Volkswagen engines is mounted in a two-piece crankcase. The halves of the crankcase are machined to very close tolerances, and should be replaced only in pairs. When fitting them, it is necessary to coat the mating surfaces only with sealing compound and tighten down to the correct torque-no gasket is used.Crankshaft
The crankshaft rests in four main bearings, and is heat-treated at all bearing points. The main bearings are of light alloy and are lead coated. The end-thrust of the crankshaft is taken up by the No. 1 main bearing (as seen from the clutch). No. 2 main bearing is of the split type-the other 3 bearings are of the one-piece type. In the engine of the beetle, the generator-fan pulley is bolted onto the crankshaft, while in the type 3 "suitcase" engine, the cooling fan is attached directly to the crankshaft. The clutch side of the crankshaft is provided with an oil seal, the fan side with an oil thrower and oil return thread. Drive gears for the camshaft and the distributor are secured to the crankshaft by means of woodruff keys.Pistons and Cylinders
The four pistons are made of light alloy and have three rings: two compression and one oil-scraping. Each piston is provided with a fully-floating piston pin secured by means of circlips. The cylinders in the Volkswagen engine are interchangeable, and can be easily replaced along with their corresponding pistons. Fins on the cylinders ensure efficient cooling of the engine.Cylinder Heads
Each pair of cylinders shares a detachable cylinder head made of light alloy casting. The cylinder head contains the overhead valves of both cylinders, and is also provided with cooling fins to further improve cooling efficiency. Shrunk-in valve guides and inserts are used. No. gasket is used between the cylinders and the cylinder head on 1963 and later engines.Connecting Rods
The four connecting rods are steel forgings and have lead-bronze bearings at the crankshaft end, while the piston pin ends are equipped with bronze bushes. The connecting rod caps are held to the rods by bolts which screw directly into the lower caps, eliminating the need for separate bolt nuts.Camshaft
Beginning with the 1966 model year, Volkswagen engines were equipped with camshafts running in three replaceable steel-backed bearings. Prior to this time, the camshaft ran in three bearings which were built into the crankcase. Because of the four-cylinder horizontally-opposed design of the engine, each of the four camlobes drives two valves, one on each side of the crankshaft. It is necessary to separate the crankcase halves in order to replace the camshaft, which is driven from the crankshaft by means of helical gears. The end-thrust of the camshaft is taken up by a special shoulder on the left-hand side of the crankcase.Valves
The overhead valves are operated by pushrods and rocker arms actuated by flat base camshaft followers.Cooling System
The air cooling system includes an oil cooler situated directly in the path of the cooling air. The presence of the oil cooler helps the Volkswagen engine to protect itself against excessively high temperatures of the internal engine parts served by the lubricating oil. The cooling fan moves a very large quantity of air in performing its very important function. For example, the cooling fan of a typical type 3 moves approximately 20 cubic feet of air each second when operating at 4000 engine rpm. When operating at cruising speed, the fan forces the equivalent of a roomful of cooling air through the engine each minute. This flow is regulated by a thermostat in order to ensure a quick warm-up, as well as efficient high-speed cooling.