Cylinder heads

The lower part of the engine houses an oil spray jet which cools the piston skirt and lubricates the grudgeon pin.

The steel, low turbulence type precombustion chambers are positioned in suitable housings and fixed by a ring nut, within which the injector is then screwed. The seatings for the heater plugs are located in the lower part of the cylinder heads; the incandescence bulb is inserted into a suitable hole in the precombustion chamber and is consequently in direct contact with the injected fuel.

In the precombustion chamber, which is shaped like two offset cylinders, the compressed air from the piston hits the conic jet of fuel injected: the front of the flame uses up the whole amount of oxygen, and continues through the sump and flows into the cylinder. In this way, combustion is rather "slow", which is indispensable if the engine is to run softly and silently.

CYLINDER HEADS

They are the monolith type, compact and chill cast in an aluminium and silicon alloy. The seatings housing the precombustion chambers and the injectors are found on the cylinder heads.

1. Heater plugs
2. Precombustion chamber with washer
3. Bushing securing precombustion chamber in cylinder head
4. Engine compression elastic sealing washer
5. Injector

The cam shaft is supported by four supports; the front and rear ones are removable and the central ones are obtained from the cylinder heads. The valve guides are fitted in the relative seatings of the cylinder heads with interference and the internal diameter is then perfected, after assembly, with a specific boring machine and checked by a pair of "fit-does not fit" gauges.

The seal between the cylinder heads and the engine block is the ASTADUR type. This seal, due to the special material from which it is made, undergoes a polymerization process when the engine is running, and hardens significantly during use; adopting this type of seal, it is no longer necessary to tighten the cylinder head at the first service.