The Lucas distributor is the heart of the MGB ignition system. A 25D4 distributor was used from 1962 to 1974 with minor variations for different engine specifications and markets, originally with a side-entry cap, changing to top-entry from the MkII in late 1967. The 45D4 was fitted from 1974 onwards on rubber bumper cars.
From 1975, North American export models with catalyst exhaust had electronic ignition using either a 45DE4 or 45DM4 distributor. The contact breaker gap was always .014, .016 inches, but dwell angle and vacuum advance curve differ depending on type and specification. Complete replacement distributors are available for 25D4 applications as new and exchange units. A 45D4 replacement for 25D applications allows an upgrade.
A 43D4 performance distributor is available with an optimised advance curve. Distributor service kits cover three production periods, pre-1967 25D4 side-entry, 1967 to 1974 25D4 top-entry, and 1974-onwards 45D4. Caps, rotors in standard and Red Rotor versions, contact sets, condensers in standard and Retronics high-quality versions, and combined condenser and Red Rotor kits are all available. Vacuum advance units cover the 25D in high and low compression specifications and the 45D in home market and export curves.
The distributor clamp, O-ring seal, vacuum pipes, and all associated fixings are available throughout.