RUNNING ADJUSTMENTS
Various adjustments are necessary from time to time in order to keep the
mechanism in efficient running order. The periods between depend largely
upon the manner in which the car is used and no definite time can be given here
for carrying out these corrections. The car should be examined however
every 5,000 miles (8,000 km.) and any adjustments which appear necessary can
then be made (see page 34).
ENGINE
Decarbonising and Valve Grinding
It is recommended that the cylinder head be removed for decarbonising and
valve grinding after the first 5,000 miles (8,000 km.). This is chiefly to give
attention to the valve seats, the metal of which becomes stabilised during this
period. Thereafter it will be found that decarbonisation will be required
only after a period of about 20,000 miles (32,000 km.). Providing that the en-
gine is running satisfactorily after this period and that each cylinder gives a
normal compression, showing that the valves are seating reasonably well, it is
much better to leave it alone and delay decarbonising for as long as the engine
continues to run satisfactorily.
The grinding of the valves becomes necessary in order not only to increase
the efficiency of
the engine, but to prevent a badly seating valve becoming worse
and getting burnt.
We recommend that the work should be carried out by the skilled mechanics
at your nearest Doretti Agent. For those who desire to do this work them-
selves, the main points to watch are outlined below
:
1.
The procedure of turning the crankshaft in order that the compression
will
"
break
"
the seal of the cylinder head should not be practised with
this design of engine.
Once the cylinder head has been removed it is important that the crank-
shaft is not rotated unless the cylinder sleeves are firmly clamped down
against their seatings. This can be accomplished by using two tubes and
washers fitted over the cylinder head studs and each secured with a cylin-
der head nut. If this precaution is not observed the sleeves may rise,
with consequent risk of water leaking into the crankcase after assembly.
On removal of the head and withdrawal of the push rods, the passage
ways in the block leading to the camshaft and thence to the crankcase and
sump must be sealed off with a clean rag or masking tape. The same
applies to the rocker shaft
oilway, both in the head and the block, to prevent
the entry of carbon particles which could do serious harm to the engine.
2. A stick of soft solder is the most suitable tool for removing the carbon. On
no account should emery cloth or sandpaper be used.
3.
It has teen found advantageous to remove the tappets and clean the insides
just prior to refitting the cylinder head to ensure that any chips of carbon
which may have fallen into the chamber are removed from the push-rod
seatings.
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