The 123 Inginition System is a complete replacement distributor, incorporating a sophisticated solid state microprocessor housed within a polished aluminium body. The processor includes 16 selectable engine series specific ignition curves, including exclusive performance curves to suit Stage II and other performance engines. Simply select the ignition curve that matches your MGs engine number for perfect timing and smooth acceleration. Delivery of the timing through a micro processor provides superior accuracy, reliability and responsiveness over standard ignition systems. A proven and simple to install performance ignition system, 123s are now fitted to thousands of MGs. Available for all classicMG models from MGA onwards, offered for positive and negative earth, with or without vacuum advance, Side or Top Entry cap.
Vacuum Advance, do I need it?
When purchasing an electronic distributor, you may notice that distributors without vacuum advance function are offered at lower cost to those with the advanced distributor function, but you should think carefully before dispensing with the vacuum advance function for a normal road going MG. The vacuum advance fitted on standard mechanical distributors and offered with electronic replacement distributors (CSI & 123) enable the distributor to deliver spark timing proportional to the load and speed output of the engine. The vacuum advance function is to provide normal road going cars with improved idle, fuel economy and throttle response delivering an improved drive particularly at lighter loads when cruising or at idle. These benefits are of little benefit for competition applications, where spark timing is delivered in proportion to speed only and not load, for these cars its fine to fit a distributor without vacuum advance.