Distributor (mechanical breaker type) - overhaul

Ignition system / Distributor (mechanical breaker type) - overhaul

Ducellier
1 The cap must have no flaws or cracks and the HT terminal contacts should not be severely corroded. The centre spring-loaded carbon contact is renewable. If in any doubt about the cap, buy a new one.

2 The rotor deteriorates minimally, but with age the metal conductor tip may corrode. It should not be cracked or chipped and the metal conductor must not be loose. If in doubt, renew it. Always fit a new rotor if fitting a new cap.

3 With the distributor removed as described in the preceding Section, take off the rotor and contact breaker.

4 To remove the contact breaker movable arm, extract the clip and take off the washer from the top of the pivot post.

5 Extract the screw and remove the fixed contact arm.

6 Carefully record the setting of the advance toothed segment and then remove the spring clip and vacuum capsule fixing screws and withdraw the capsule with link rod.

7 Pick out the lubrication pad from the recess in the top of the distributor shaft. Unscrew the screw now exposed.

8 Mark the relationship of the cam to the counterweight pins and then remove the cam assembly.

9 There is no way to test the bob weight springs other than by checking the performance of the distributor on special test equipment, so if in doubt, fit new springs anyway. If the springs are loose where they loop over the posts, it is more than possible that the post grooves are worn. In this case, the various parts which include the shaft will need renewal. Wear to this extent would mean that a new distributor is probably the best solution in the long run. Be sure to make note of the engine number and any serial number on the distributor when ordering.

10 If the mainshaft is slack in its bushes or the cam on the spindle, allowing sideways play, it means that the contact points gap setting can only be a compromise; the cam position relative to the cam follower on the moving point arm is not constant. It is not practical to re-bush the distributor body unless you have a friend who can bore and bush it for you. The shaft can be removed by driving out the roll pin from the retaining collar at the bottom. (The collar also acts as an oil slinger to prevent excess engine oil creeping up the shaft.)
Marelli
11 With the distributor removed from the engine, take off the spark shield and rotor.

12 Remove the contact breaker and carrier as described in Section 2.

13 Refer to paragraphs 9 and 10 for details of counterweight springs and shaft bushes (photo).

7.13 Marelli distributor centrifugal weights and springs

Reassembly
14 This is a reversal of dismantling. On Ducellier distributors, make sure that the advance toothed segment is returned to its original setting otherwise the advance curves for your particular engine will be upset.

Fig. 4.6 Exploded view of typical Ducellier distributor (Sec 7)

1 Cap
2 Rotor
3 Movable breaker arm
4 Vacuum advance link
5 Fixed contact breaker arm 6 Contact breaker baseplate 7 Cam assembly
8 Centrifugal advance weight control springs 9 Driveshaft and plate
10 Body
11 LT insulator
12 Condenser
13 Vacuum capsule
14 Cap retaining spring
15 Thrust washer
16 Spacer washer
17 Driving dog
18 Retaining pin
19 Felt pad