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encountered, but replace the cylinder head in boiling water for a further
two minutes
(f) When pressing out the guides ensure that the punch does not score or
damage the bores in any way Failure to observe this precaution may
result in the new guides being loose in the cylinder head.
34. To replace valve guides
(a) Before fitting new guides, ensure that the bores in the cylinder head
and the body of the guides are clean.
(b) Place the cylinder head in boiling water for two minutes, enter the
guides squarely in the bores from the rocker box side, and press home
to the shoulder
(c) If a press is not available, a drift may be used, but SPECIAL CARE
MUST BE TAKEN to avoid the drift slipping, scoring or otherwise
damaging the bores
(d) The valve guides MUST NOT BE REAMED.
(e) Grind in the valves
35. To grind in valves
(a) Care must be taken that the valves are returned to their correct seating
for this operation
(b) Place a very small quantity of grinding paste evenly around the valve
seat and insert the valve Partially rotate the valve backwards and
forwards on its seating, exerting a gentle but firm pressure
(c) Periodically lift the valve from its seating and give it half a turn. Thus
ensuring that the grinding paste is evenly spread
(d) It is unnecessary to continue grinding once the faces of the valve and
its seating have a clean, even. matt-surfaced appearance. A polished
surface must not be expected and is unnecessary
(e) Wash out the ports thoroughly with petrol or paraffin making sure that
all traces of grinding paste are removed from the valves and guides
(f) Replace the valves and rotate them backwards and forwards a few
times If the valves have been correctly ground a thin polished line will
appear all round the seat.
36. To replace cylinder head
(a) Generally reverse the instructions for removal and dismantling. The
rocker bushes and push rod ends should be smeared with
molybdenum-disulphide grease before assembly
(b) It is IMPORTANT that the exhaust and inlet valves be returned to their
correct positions
(c) If the valves are distorted or very badly pitted, fit new ones
(d) If new valves or guides are fitted, the valves must be ground in.
(e) Whenever the cylinder head is removed after the engine has been run,
a new gasket MUST be fitted.
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