Model DVX4A (Lucas part number 409929, later replaced by 40112A and 401091) with automatic advance (centrifugal and vacuum operated) and vernier adjustment. Driven by skew gear from camshaft, counter-clockwise rotation.
| Lucas Part No. | Type | E.C.M. Curve No. | Range |
|---|---|---|---|
| 40112A | BS49 | 371 | 16°-18° |
| 409929 | BS36-1 | 344 | 17.1/2°-20° |
Centrifugal advance range from 32° to 36° (on crankshaft rotation), beginning at 840 to 1240 rpm with maximum advance at 3880 to 3920 rpm.
Firing point at 11° BTDC.
Contact breaker set at 0.012" (with points fully open).
Replacement Lucas part numbers DSB122 (contacts) (was 407050), DCB121 (condenser) (was 407044), DDB163 (cover) (was 415298).
Check contact points break at 11° before TDC, an 'IGN' mark being visible on the flywheel, visible through the gearbox inspection cover.
Every 3,000 miles:
Give the cam and the pivot on which the contact breaker rocker arm works a light smear of grease or clean engine oil.
Withdraw the moulded rotor arm from the top of the spindle by pulling it off, and add a few drops of thin machine oil. Do not remove the screw exposed to view, as there is a clearance between the screw and the inner face of the spindle through which the oil passes to lubricate the cam bearing. Take care to refit the arm correctly and to push it on to the shaft as far as possible, otherwise there is a risk of tracking and burning of the moulding.
Add a few drops of thin machine oil to the oil reservoir through the hole in the contact breaker base. Do not allow any oil to get on to the contacts.
Distributor housing may resist movement due to build up of grease and dirt, in which case a sharp tap from the underside should dislodge it.
If distributor is free moving but cannot be removed more than 1/4" from housing, the cause may be a slipped pin (in the shaft, just below the housing) catching on the housing. The housing must also be removed.
The spring clips which hold the distributor cap have been known to become brittle and snap. They may also come loose, or fall off, usually as a result of damage to the folded metalwork which holds the pins on which the clips rotate.
1) Note the direction of the rotating arm before removal, as it is possible to replace the distributor with the arm 180° from its correct position.
2) Either |
a) loosen the pinch bolt (horizontal bolt at base of distributor, right side), b) remove one dowelled screw, holding the clamp to the housing, c) remove two 1/4" setscrews at left and right of housing |
3) Pull and twist to remove the distributor.
Distributor cap FC1265 (from FC Ignition Replacements) may be a suitable replacement part (it is listed as replacing Lucas part number 408369 and not 415298 however).
The Remax condenser (part number ES96) and contacts (part number ES79), are a suitable alternative. However, since Lucas condenser and contacts were fitted to some Jaguar cars, spare parts should be readily available.
Greyfriars contact set 050 is listed as a suitable replacement.
Remax part number ES214 is a suitable distributor cap replacement. The Lucas part was also fitted to Land Rovers.
A Lucas Model D3A4 (service number 40341D) distributor, as fitted to several 1950's tractors, has successfully been used as a replacement, although it has no automatic advance mechanism.
It is possible to upgrade to electronic ignition with the Aldon, positive earth igniter unit (exact model number unknown).
Lucas points, part #DSB 122, can be substituted with a little modification - cut off the end and grind a slot as per the original points.
Although the Sunbeam Talbot 2 litre (1946), Austin A90 (1949-1952), Lea Francis 14 (later) (1953-1954), and Lanchester 14 (1952-1953) were also fitted with a DVX4A, they were Lucas service numbers 40061, 40172, 40245, and 40294 respectively. The differences lie mostly in the E.C.M. curves and range, although some were clockwise rotation.
For a detailed breakdown of components and Lucas part numbers, see this link.