Due to the relatively inaccessible situation of the power unit in the Mini, few repair operations can be easily and successfully carried out while the unit is still in the car. The obvious exception is any work concerning the cylinder head. The timing cover, timing chain and gears can be replaced with the engine in place, but only with difficulty.
Clutch replacement can be carried out once the righthand end of the engine/transmission unit has been raised, and involves removal of the clutch cover and the flywheel assembly to gain access.
Once the unit has been lifted out of the car it is a relatively simple job to separate the engine from the gearbox casing. The clutch cover, clutch and flywheel assembly and flywheel housing however must first be removed.
VALVE CLEARANCES The rocker cover must first be removed. Where fitted, release the three clips and remove the ignition shield from the front of the engine. If necessary, remove the air cleaner assembly after disconnecting the breather hose (when fitted). Remove the two retaining nuts together with their cup washers and seals and lift off the rocker cover and gasket .
It will facilitate turning over the engine if the spark plugs are removed at this point. Suitably label the plug leads to ensure they will be reconnected correctly.
The valve adjustments should be made with the engine cold. The importance of correct rocker arm/valve stem clearances cannot be overstressed as they vitally affect the performance of the engine. If the clearances are set too wide, the efficiency of the engine is reduced as the valves open late and close earlier than was intended. If, on the other hand the clearances are set too close there is a danger that the stems will expand upon heating and not allow the valves to close properly which will cause burning of the valve head and seat, and possible warping.
For this operation the engine can be turned over by engaging reverse gear and pushing the car backwards, or by jacking one of the front wheels clear of the ground and rotating the wheel. In this latter case, top gear should be engaged. On automatic models use a screwdriver inserted through the aperture in the converter housing to rotate the converter by levering on the ring gear. Crankshaft rotation is clockwise, viewed from the radiator end of the engine.
Rotate the crankshaft until each valve in turn listed in the left-hand column below is fully open (spring compressed), then check the clearance of the valve listed opposite in the right-hand column. Valve numbering is from the radiator end of the engine.
Valve No. 1 open check valve No. 8
Valve No. 3 open check valve No. 6
Valve No. 5 open check valve No. 4
Valve No. 2 open check valve No. 7
Valve No. 8 open check valve No. 1
Valve No. 6 open check valve No. 3
Valve No. 4 open check valve No. 5
Valve No. 7 open check valve No. 2
The valve rocker clearance should be 0.012 in (0.305 mm) for both the inlet and exhaust valves (cold). The clearance is correct when the appropriate thickness of feeler gauge is a neat sliding fit between the end of the valve stem and the pad on the rocker arm.
If adjustment is necessary, slacken the adjusting screw locknut with a ring spanner, and turn the adjusting screw on the push rod end of the rocker arm until the correct gap is obtained . Turn the screw clockwise to reduce the clearance, or anti-clockwise to increase it. Retighten the locknut while holding the adjusting screw with the screwdriver to prevent it turning, then recheck the gap.
When adjustment is complete, refit the rocker cover. Use a new cork gasket if necessary. Ensure that all traces of old gasket have been removed from the cover and cylinder head mating faces before fitting. Tighten the cover retaining nuts evenly to ensure a good seal.
Refit the spark plugs, if removed, and reconnect the plug leads. Finally, refit the air cleaner, if removed.