The ignition system uses a conventional coil, distributor, and contact breaker arrangement as original equipment. The 1275cc and the 1500 use entirely different distributor types with no shared internal components, so identifying the correct distributor is essential before ordering any ignition parts.
Distributor Types
Two Lucas distributor types were fitted: the 25D4 with a side-entry distributor cap on 1275cc engines, and the 45D4 with a top-entry cap on 1500 engines. The two distributors use different caps, rotor arms, contact breaker point sets, and condensers, none are interchangeable between the two types. Contact breaker points, condensers, rotor arms, and distributor caps are routine service items. Vacuum advance units are specific to each distributor and are available as individual replacements.
Exchange reconditioned distributors are available for owners whose distributor body or shaft is worn beyond adjustment.
Ignition Coil
The ignition coil must be matched to the car's earth polarity, positive-earth and negative-earth coils have their internal windings connected differently. Fitting the wrong polarity coil produces a weak, reversed-polarity spark that causes difficult starting and persistent misfiring under load. The coil terminal markings (SW and CB, or + and -) must correspond to the correct connections for the car's polarity.
HT Leads and Spark Plugs
HT lead sets are specific to the distributor type. The 25D4 lead set is available in two variants: screw-type coil connection and push-fit coil connection, so the coil fitted to the car determines which lead set is required. The 45D4 uses its own lead set. Standard copper-core leads are available, and silicone HT leads provide superior insulation and heat resistance, a worthwhile upgrade on any car, and essential on those suffering from misfiring in damp conditions where the original leads' insulation has deteriorated.
Spark plugs differ between the 1275cc and the 1500, reflecting the different combustion chamber designs and compression ratios, the correct specification for each engine must be confirmed when ordering.
Electronic Ignition Conversions
Electronic ignition conversions eliminate the contact breaker points entirely, providing maintenance-free operation, improved spark consistency across the rev range, and easier cold starting. The Lumenition Optronic uses an optical trigger fitted inside the original distributor body, retaining the external appearance of the standard unit. A Lumenition Magnetronic (magnetic trigger) is also available for both distributor types. The Lumenition High Performance Kit adds a performance coil and uprated amplifier for engines producing significantly more than standard power.
For negative-earth 1275cc cars and all 1500 models, these conversions are among the most cost-effective upgrades available. A 123 Ignition complete replacement distributor with selectable advance curves is available for the 45D4 (1500), replacing the entire distributor assembly with a self-contained electronic unit.