This blog, in addition to the usual maintenance details for classic mini cars, an attempt is made to explain the "whys" and "wherefores" of the various jobs.

Saturday, 17 October 2009

Replacing the Cylinder Head

Before refitting the cylinder head make sure that the piston crowns, cylinder walls, and the top of the block are scrupulously clean. Pour a small quantity of engine oil around each bore so that it will be distributed over the cylinder walls and down the sides of the pistons when the engine isv first turned over.

The new cylinder-head gasket is marked "Front" and "Top" to ensure correct assembly. Never use gasket cement, as this is Likely to cause subsequent leakage. The five cylinder-head retaining nuts should be tightened only finger-tight at this stage.

Place the eight push-rods in position, making sure that they locate in their respective tappets, and place the rocker shaft assembly on the studs. Carefully work it into position, making sure that the rocker adjusting screws engage properly in the push-rod cups. Tighten the nuts down evenly, finger-tight, and then tighten all nine nuts progressively with a spanner in the order shown in Fig. 22.

Adjust the valve clearances as described on pages 43-4. The remainder of the reassembly is quite straightforward. The cable-abutment plate fitted between the carburettor and the manifold flange should have a gasket on each side. Renew these if the original gaskets are damaged.

After a final check all round, refill the cooling system and start the engine.

If a heater is fitted, check the level of the water in the header tank after the engine has been running for a few minutes. When the engine is well warmed-up, switch off and go over the cylinder-head and manifold nuts again. The nuts should be checked a second time after about 300 miles running. Remember to readjust the valve clearances on each occa¬sion, as they will be reduced when the cylinder head is pulled down.

When the engine has been decarbonized the ignition timing should be checked as described in Chapter 7. It is usually possible to advance the ignition slightly. Also, the carburettor slow-running mixture strength and speed will usually require readjustment, as described.