Performance and electronic distributors are the complete-replacement alternative to retrofit electronic ignition. Where retrofit conversions replace the points-and-condenser inside an existing Lucas distributor body, performance distributors replace the entire distributor, the shaft, bearings, cam, mechanical advance weights, points or their electronic equivalent, condenser, and body, with a modern unit that offers programmable timing curves, integrated electronics, and substantially better reliability than the rebuilt original. The mechanical advance weights and springs in an original Lucas distributor are a known source of timing inconsistency as they wear, the weights sticking and the springs fatiguing so the advance curve drifts from the original specification, and a complete electronic distributor eliminates this with electronic advance curves that never change.
For owners who want the best ignition system available on a classic MG, a programmable electronic distributor is the appropriate upgrade.
123ignition & CSI
Two principal brands cover the programmable-distributor market for classic British cars. The 123ignition distributor is a complete replacement unit housed in a polished aluminium body, fitted with a solid-state microprocessor that handles timing and advance digitally rather than through mechanical weights and a vacuum capsule, carrying sixteen selectable engine-specific ignition curves chosen via a rotary switch on the body, including exclusive performance curves to suit Stage II and other modified engines, with the owner simply selecting the curve matching the engine specification. The CSI distributor offers the same solid-state advance control but housed within an original Lucas-style body, so the visual appearance matches the factory distributor closely and the car retains a period-correct engine-bay appearance while running fully modern internals, the selectable curves concealed beneath the cap, making it the ideal choice for owners restoring cars for concours purposes who want modern ignition reliability without the visual compromise of an external aluminium body. Both are available in positive and negative earth, with or without vacuum advance, and in the cap-entry configuration matching the original distributor fitment, and both are maintenance-free with no wearing parts and no need for re-curving in normal road use.
What the Programmable Curve Provides
The advance curve on a Lucas distributor is determined by the mechanical bob-weights and springs inside the body, which swing outwards under centrifugal force as engine speed rises, advancing the timing through a set mechanical curve specified for the original engine and unchangeable without physical modification. A programmable distributor allows the curve to be set electronically, typically specified by initial advance at idle, maximum advance at full rev, and the rate at which the advance comes in between those points, with the microprocessor also adjusting dwell angle throughout the rev range for peak spark energy at every engine speed, something a points-type distributor cannot do as its dwell is fixed. For a standard engine the appropriate curve matches the original Lucas specification, while for tuned or modified engines the curve can be customised, typically more advance at part-throttle for cruising economy or a faster advance ramp for acceleration response, making the programmable distributor one of the most worthwhile single upgrades for cars built to high specifications.
Complete & Reconditioned Units, Installation
Alongside the programmable electronic distributors, complete replacement distributors are available in standard and performance specifications for owners stepping up from a worn original, including the option for owners of earlier cars to move from the 25D4 to the more robust 45D4 type, and reconditioned exchange units where the existing distributor is beyond economical repair, the customer's old unit returned as the core. The choice between a complete electronic distributor and a conversion kit fitted to the existing unit is largely a matter of budget and the condition of the existing distributor, a conversion kit being better value where the mechanical components are sound and a complete replacement the better investment where they are worn. Installation replaces the original distributor in its existing mounting, the new shaft engaging the existing drive gear and the wiring connecting to the existing coil terminals, after which the timing is verified with a strobe light, the advance curve on a performance distributor needing to match the rest of the engine specification, the fuel system, exhaust, camshaft, and cylinder heads, to give a balanced result, as an over-aggressive curve on a standard engine causes pinking under load while a mild curve on a performance engine wastes the engine's potential.