The engine controls group covers the link between the accelerator pedal and the twin SU carburettors, the throttle cable and operating linkage, the choke (mixture) control cable, the accelerator pedal, and the return springs that close the throttles. Keeping these components in good order is essential for crisp throttle response, a reliable cold start, and a throttle that returns cleanly to idle.
Accelerator Pedal
The MGA uses a floor-mounted, organ-type accelerator pedal that pivots at the toe-board. The pedal pad and pivot are simple, hard-wearing items, but the pad rubber perishes and the pivot can stiffen or wear over time. The pedal acts on the throttle linkage that carries the movement back to the carburettors.
Throttle Cable & Linkage
The throttle is operated through a cable and bellcrank linkage that opens both SU carburettors together. The standard MGA 1500, 1600, and Mk II cars use twin SU H4 carburettors, while the Twin Cam uses the larger HD6, so the linkage and abutment details should match the carburettors fitted. A correctly set-up linkage opens both throttles in unison and allows them to return fully to the idle stops.
Choke / Mixture Control
A dash-mounted choke control operates the carburettor jet levers through a cable to richen the mixture for cold starting. The inner cable, outer casing, and the clamp at the carburettor end are all serviceable, a stretched or seized choke cable is a frequent cause of difficult cold starts and a fast idle that will not return to normal.
Throttle Return Springs
Return springs close the throttles cleanly when the pedal is released. Weak or missing springs allow the idle to hang and are a safety concern, and should be checked whenever the linkage is disturbed.
The MGOC Spares range covers accelerator pedals and pads, throttle cables, choke (mixture) control cables, the throttle linkage and return springs, together with the clips and fixings needed to set the controls up correctly.