Page 34 - Demo

Page 34.Alvis Three Litre Shop Manual - T.A. 21 and T.C. 21stem as possible. When the valve spring has been compressed sufficiently to enable the rocker to be disengaged from the push rod cup, slide the rocker to one side and withdraw the push rod and return spring. This operation is made easier by slackening off the valve clearances to the full extent before attempting to withdraw the push rods.Remove the cylinder head nuts, the rocker shaft, and cylinder head. Place the cylinder head on a bench and remove the valve springs, and valves.Vaalvve RRemmovavalThe valve springs are retained by split collars and may be compressed by the normal type of valve spring compressor. A far easier method is to use a special ALVIS valve spring compressor which utilises the rocker shaft as a fulcrum point. A flat board with six wooden blocks screwed to it, to register with the combustion chambers, should be placed under the cylinder head face and six long bolts passed through the cylinder head to secure the rocker shaft centre and end brackets. Each valve spring can then be compressed in turn and the collars withdrawn, the valve being held in place by the wooden blocks.Care should be taken to segregate the valves to ensure that each valve is replaced on its own particular seating. It should also be noted that one half collar on each inlet valve is rubber faced forming an oil seal to prevent excessive oil passing down the valve stem.Vaalvve GriindiinggRemove all traces of carbon from the combustion chambers, exhaust ports, valves, and piston crowns. Insert each valve in its respective guide and grind in each in turn. Smear a little coarse grinding paste on the valve seating- and with the aid of a tool attached to the stem rotate the valve alternately in both directions, occasionally lifting it off its seating, until a dull grey unbroken ring has formed on both the valve head and its seating in the cylinder head. Impart a final finish by using a fine grade of paste, and then, when all the valves have been ground in, thoroughly wash the cylinder head and valves in paraffin. Smear the valve stems with clean engine oil and refit into the cylinder head.Cyliinder HHeaad RRepplacacemmenttRefit the cylinder head in the reverse order to stripping, using all new gaskets and joints. To ensure that a good joint is made, apply shellac or some other jointing compound to both sides of the cylinder head gasket, and place the gasket on the cylinder block so that the cut-away portion at the edge lines up with the distributor cut-away in the top faces of the block. Tighten down the cylinder head nuts, working alternately from one side to the other, starting in the centre and finishing at both ends.After valve grinding it will of course be necessary to reset the valve clearances before running the engine. It is advisable to give a little more clearance to allow the valves to bed in during the first few miles of running, after which the clearances may be adjusted to the normal 0.009%u201d, when the engine is warm. When this is being done the opportunity should be taken to check the tightness of all the cylinder head and manifold nuts.Vaalvve Geaar Mai ainttenaancceEVERY 2,000 MILES (3,200 K.M.). %u2013 Check valve clearances.EVERY 10,000 MILES (16,000 K.M.). %u2013 De-carbonise engine and grind in valves.