Removing And Replacing The Distributor; Static Ignition Timing - MG MGA Twin Cam Workshop Manual

The moving contact can be removed from its mounting to assist cleaning. Check and adjust
the contact breaker setting after cleaning the contacts.
3. Check that the moving arm is free on its pivot. If it is sluggish, remove the arm and polish the
pivot pin with a strip of fine emery-cloth. Afterwards clean off all trace of emery dust and apply
a spot of clean engine oil to the top of the pivot. The contact breaker spring tension should be
between 20 and 24 oz. (567 and 680 gm.) measured at the contacts.
Fig. B.2 The arrows indicate the fixed contact plate securing screw and the adjusting notch
B.6 REMOVING AND REPLACING THE DISTRIBUTOR
The distributor can be removed and replaced without interfering with the ignition timing, provided the
clamp plate pinch-bolt is not disturbed.
To facilitate the replacement of the distributor, remove the distributor cover and turn the engine over
until the rotor arm is in a position pointing to the segment for No. 4 cylinder plug lead to provide a
datum for replacement.
Disconnect the low-tension lead from the terminal on the distributor. Disconnect the suction advance
pipe at the union on the distributor.
Extract the two bolts securing the distributor clamp plate to the distributor housing and withdraw the
distributor.
To replace the distributor insert it into the distributor housing until the driving dog rests on the
distributor drive shaft. The rotor arm should then be rotated slowly until the driving dog lugs engage
with the drive shaft slots, both of which are offset to ensure correct replacement. Turn the distributor
body to align the clamping plate holes with those in the housing. The remainder of the assembly is
now in the reverse order to that of removal.
NOTE: Provided that the crankshaft has not been turned, the rotor arm will be opposite the segment
for No.4 plug lead. The high-tension leads can then be replaced on their respective plug terminals in
the order of firing, i.e. 1,3, 4, 2, remembering that the distributor rotation is anticlockwise when viewed
from above.
B.7 STATIC IGNITION TIMING
The ignition timing must be set to satisfy the requirements of the grade of fuel used. (See "GENERAL
INFORMATION'.)
After timing the ignition, it is essential that the distributor advance mechanism be checked as
described in Section B.13.
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