Fiat Uno Manual

Cylinder head - removal and refitting (903 cc engine)
Engine / Cylinder head - removal and refitting (903 cc engine)


1 For safety reasons, disconnect the battery negative lead.

2 Refer to Chapter 2 and drain the cooling system.

3 Refer to Chapter 3 and remove the carburettor, air cleaner and spacer block.

4 Undo and remove the five nuts and washers securing the exhaust manifold and hot air ducting to the cylinder head.

5 Detach the cable from the temperature indicator sender unit.

6 Refer to Chapter 4 and disconnect the distributor LT lead and the coil HT lead.

7 Refer to Chapter 2 and remove the thermostat housing from the cylinder head.

8 Disconnect the coolant hoses from the cylinder head.

9 Note the electrical connections to the rear of the alternator and disconnect them.

10 Disconnect the mounting and adjuster link bolts and remove the alternator from the engine.

11 Unscrew the four nuts securing the rocker cover to the top of the cylinder head and lift away the spring washers and metal packing pieces. Remove the rocker cover and cork gasket.

12 Unscrew the four rocker pedestal securing nuts in a progressive manner. Lift away the four nuts and spring washers and ease the valve rocker assembly from the cylinder head studs.

13 Remove the pushrods, keeping them in the relative order in which they were removed.

The easiest way to do this is to push them through a sheet of thick paper or thin card in the correct sequence.

14 Unscrew the cylinder head securing bolts half a turn at a time in the reverse order to that shown in Fig. 1.7; don’t forget the one within the inlet manifold. When all the bolts are no longer under tension they may be unscrewed from the cylinder head one at a time. This will also release a section of the cooling system pipe secured by two of the bolts. All the bolts have washers.

15 The cylinder head may now be lifted off. If the head is jammed, try to rock it to break the seal. Under no circumstances try to prise it apart from the cylinder block with a screwdriver or cold chisel as damage may be done to the faces of the head or block. If this or the Hint, fail to work, strike the head sharply with a plastic headed hammer, or with a wooden hammer, or with a metal hammer with an interposed piece of wood to cushion the blows. Under no circumstances hit the head directly with a metal hammer as this may cause the casting to fracture. Several sharp taps with the hammer, at the same time pulling upwards, should free the head. Lift the head off and place on one side.

16 The cylinder head may now be decarbonised or dismantled, refer to Section 17.

Refitting
17 After checking that both the cylinder block and cylinder head mating surfaces are perfectly clean, generously lubricate each cylinder with engine oil.

18 Always use a new cylinder head gasket as the old gasket will be compressed and not capable of giving a good seal.

19 Never smear grease on the gasket as, when the engine heats up, the grease will melt and may allow compression leaks to develop.

20 The cylinder head gasket cannot be fitted incorrectly due to its asymmetrical shape, but the word ALTO should be uppermost in any event (photo).

7.20 Cylinder head gasket
7.20 Cylinder head gasket

21 The locating dowels should be refitted to the front right and left-hand side cylinder head securing bolt holes.

22 Carefully fit the cylinder head gasket to the top of the cylinder block.

23 Lower the cylinder head onto the gasket, taking care not to move the position of the gasket.

24 Screw in the cylinder head bolts finger tight, remembering the bolt within the intake manifold and the metal coolant pipe which is held by the two cylinder head bolts adjacent to the coolant temperature sender unit (photos).

7.24A Cylinder head bolt in intake manifold
7.24A Cylinder head bolt in intake manifold

7.24B Cylinder head bolts holding coolant pipe
7.24B Cylinder head bolts holding coolant pipe

25 Tighten the cylinder head bolts in two stages, in the specified sequence to the torque given in Specifications.

26 With the cylinder head in position, fit the pushrods in the same order in which they were removed. Ensure that they locate properly in the stems of the tappets and lubricate the pushrod ends before fitment (photo).

7.26 Fitting a pushrod
7.26 Fitting a pushrod

27 Unscrew the rocker arm adjuster screws as far as they will go.

28 Fit the rocker gear over the four studs in the cylinder head and lower onto the cylinder head. Make sure the ball ends of the rockers locate in the cups of the pushrods.

29 Fit the four nuts and washers to the rocker shaft pedestal studs and tighten in a progressive manner to the torque wrench setting given in the Specifications.

30 Adjust the valve clearances as described in Section 5.

31 Fit the exhaust manifold, thermostat housing and alternator, also the rocker cover (photo).

7.31 Fitting the rocker cover
7.31 Fitting the rocker cover

32 Fit the carburettor, air cleaner and distributor (Chapter 4).

33 Reconnect all hoses and electrical leads, including the battery.

34 Refill the cooling system.

Fig. 1.7 Cylinder head bolt tightening sequence (Sec 7)
Fig. 1.7 Cylinder head bolt tightening sequence (Sec 7)


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