Rolls-Royce Silver Shadow
B
Bentley
T
Series
Workshop
Manual
Chapter
K
Carburetters
-
To
set
Cars prior
to
Car serial Number
SRH
8742
Having set the mechanical adjustments to the auto-
matic choke set the carburetters by carrying out the
following operations (where applicable) in the
sequence given.
The correct method for carrying out the operations,
follows the undermentioned list.
A
Synchronise throttles and temporarily set the
throttle stop screw.
B
Set the full throttle stop.
C Check the linkage clearances.
D Tune the carburetters.
E
Set the cold start 'fast-idle'.
F
Set the throttle damper plunger (if fitted).
G
Set the stator micro-switches (if fitted).
H
Set the kick-down micro-switch (if fitted).
I
Set the refrigeration 'fast-idle' (if fitted).
Throttle synchronisation
1. Check that the fixed throttle stop screw is set to
the correct dimension; refer to the appropriate illustra-
tion (see Figs.
K20
and
X21
diagrum
C
dimension
Y).
2.
Unscrew the four screws securing the suction
chamber of each carburetter and remove the suction
chambers together with the pistons, springs and
dampers.
Note
It is important that each chamber and air
valve piston should be fitted to the
car-
buretter from which it was removed.
3.
Slacken the two pinch bolts which clamp the
operating levers to the throttle spindles (see Figs.
K20
and
K21).
4.
Ensure that the choke is in the off position; an
elastic band fitted between the choke link rod and the
crankcase breather pipe fitting on the choke housing
will serve to hold the choke in the off position.
5.
With the 'A' and
'B'
bank throttle butterfly
valves held in the closed position, move the
'A'
bank
throttle lever so that it abuts its stop; tighten the two
pinch bolts which clamp the operating levers to the
throttle spindles.
6.
Check that both throttle butterfly valves are
closed.
7.
Release the idle stop screw lock-nut, then turn
the screw clockwise (downward) half-a-turn so that
the throttle butterfly valves are just cracked open;
tighten the lock-nut.
8.
Final adjustment of the idle stop screw should
be carried out as described in 'Carburetter Tuning'.
9.
Cars prior to Car Serial Number
SRX
9001.
If a
refrigeration vacuum
unit (see Fig.
K2I)
is fitted, set
the gap between the vacuum unit shaft and the adjust-
ment screw to
0.100 in. (2,54 mm.).
Cars from Car Serial Number
SRX
9001
and
onwards fitted with the Exhaust Emission Control
System.
Set the gap between the throttle stop vacuum
actuator shaft and the adjusting screw to
0.070 in.
(1,78 mm.).
Full throttle stop
1. Adjust the full throttle stop screw so that it is
set to the dimension given on the appropriate
illustra-'
tion (see Figs.
K20
and
K21
dimension
W).
2.
Check that the clearance
(X)
between the fixed
stop and the lever is correct (see appropriate illustra-
tion Figs.
K20
and
K21).
If the clearance is
less
than
that which is given, the full throttle stop screw should
be adjusted to give the correct clearance.
Linkage clearances-To check
1. Operate the carburetter linkage mechanism to
ensure complete freedom of movement.
2.
Particular attention should be paid to the clear-
ance between the
'9'
bank carburetter float chamber
and the refrigeration 'fast-idle' adjusting screw on
early cars (if fitted) or the vacuum throttle stop screw
on later cars (if fitted); the clearance at this point when
the linkage is moved towards its full throttle position
should be at least
0.100 in. (2,54 mm.). If less than
this figure, the four screws securing the float chamber
to the carburetter body should be slackened and the
chamber moved outward until the correct clearance is
established; tighten the four screws. This dimension is
applicable to both early and late linkage arrangements
and is shown in Figure
K21,
clearance
2.
Carburetter tuning
Cars prior
to
Car Serial
Number
SRH
8742
Preliminary checks
Before tuning the carburetters the following checks
should be carried out.
1.
Check that the distributor contact point gaps are
set correctly; if necessary clean and reset.
2.
Check the sparking plug gaps.
3.
Check the ignition timing, refer to Chapter
M-
Electrical System.
4. Check that the entire induction system is
corn-
pletely free from air leaks.
5.
Check that the choke stove pipe is not obstructed
(see Page
K27).
6.
Ensure that the throttle damper is not holding the
throttles open.
7.
Ensure that the throttle butterfly valves are
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