Lotus TURBO ESPRIT Service Manual page 170

Page
28
SECTION EA
Remove a l l carbon deposits from +he cylinder head combustion chamber faces,
inlet and exhaust ports, piston crowns and valve heads. A ring of carbon
should be left around the periphery of each piston crown. The
TOP
of the
cylinder liners should
NOT
be touched.
Clean each valve thoroughly and carefully examine for pitting. Valves i n a
pitted condition should be refaced with a suitable grinder or new valves should
be fitted.
If
the valve seats show any signs of pitting, or uneveness, they shduld
be trued by the use of service cutting tools. When using a cutting tool take care
to remove only as much metal as i s necessary to ensure a true surface. The removal
of too much metal could cause difficulty i n achieving the required valve
clearance.
When grinding a valve onto its seating the valve should be smeared lightly
with 'fine' or 'medium' carborundum paste and then lapped i n with a suction
type grinder after oiling the valve stem. Avoid the use of excessive quantities
of grinding paste and ENSURE that i t remains i n the region of the valve seating
only. A light coil spring placed under the head of the valve w i l l assist
considerably i n the process of grinding. The valve should be ground to its
seat with a semi-rotary motion and occasionally allowed to rise by the pressure of
the light coil spring.
This
action assists i n speeding the grinding operation until
a dull, even, matt finish, free from any blemishes i s achieved on the valve seat
and valve face. On completion, the valve seats, guides and ports, should be
cleaned with petrol then blown dry and clean with compressed air. The valves
should be washed i n petrol and a l l traces of grinding paste removed. Ensure that
no grinding paste has entered the valve guides.
Lightly
oil
the valve stems, and re-assemble the valves to cylinder head.
Refit cylinder head, camshaft housings not forgetting to check the valve
clearances, camshaft coven, inlet and exhaust manifolds, carburetters, etc
.
,
EA.13.
-
VALVE SEAT INSERTS
To
Remove
1
.
Remove the cylinder head and dismantle as for decarbonising (Section
EA
.12
.)
2.
Remove the valve seat inserts by milling through, or almost through (dependant
upon the
skill
of the operator), the edge of the insert, whereupon the seat should