INTRODUCTION - CYLINDER HEAD(S)

1.2 8v

CONSTRUCTION SPECIFICATIONS

The cylinder head is a one-piece cylinder head made from aluminium alloy. The two valves per cylinder are fitted in the guides, operated by a camshaft by means of mechanical tappets with cups and adjustment shims.

The valve guides are press-fitted into the relative cylinder head seats with interference.

A special reamer is used to produce the correct inner diameter after fitting.

The gasket between cylinder head and crankcase is made out of aramid fibre and the head does not require retightening throughout the engine life.

COMPOSITION

The elements that make up the cylinder head are as follows:

• camshaft
• camshaft mounts
• tappets
• pipe for lubrication
• intake and exhaust valves
• valve guides
• valve seat
• tappet cover
• air intake and exhaust manifold studs

The head contains: the intake ducts (with a Venturi pipe shaped profile) (1); exhaust ducts; valve passage ports; coolant passage ports; lubricant passage ports; threaded openings for the spark plugs, openings for fastening to the engine block and the combustion chambers.

A. Inlet duct

B. Exhaust duct

OPERATION

The function of the cylinder head is to close the cylinder; it contains the combustion chambers where the fuel/ air mix is compressed and ignited. Extremely high temperatures are reached here (average temperature ~2300 °C). This is why the cylinder heads are made using aluminium alloys with properties of lightness, resistance to compression and high thermal conductivity.

The use of this material allows the compression ratio to be increased to make knock less likely because heat is dissipated more quickly from hot spots.

HEAD COVER

The head cover is made from aluminium alloy; a variable valve timing control solenoid is fitted to the cover.

1. Head cover

2. Oil filler cap

3. Variable valve timing solenoid

4. Oil vapour recovery connector

1.4 16v

CONSTRUCTION SPECIFICATIONS

The cylinder head is a one-piece cylinder head made of aluminium alloy.

The four valves per cylinder are fitted in the guides, operated by two camshafts by means of hydraulic tappets.

The valve guides are press-fitted with interference in their seats on the cylinder head.

A special reamer is used to produce the correct inner diameter after fitting.

The camshafts are fitted in two built-in cylinder heads, without a tappet cover.

The gasket between cylinder head and engine block is a double layer metallic gasket, 0.5 mm thick; the head does not require retightening throughout the engine life.