The MGB GT V8's engine controls connect the driver's throttle pedal and choke knob to the twin SU HIF6 carburettors mounted at the rear of the engine. Because the carburettors sit at the rear of the V, rather than at the side as on the four-cylinder MGB, the throttle and choke cable runs are V8-specific and are not interchangeable with four-cylinder MGB items. The general arrangement uses cable-operated throttle and choke linkages to a balance bar that synchronises the two carburettors, ensuring both throttle butterflies open together for smooth running.
Throttle Cable and Linkage
The throttle cable runs from the driver's throttle pedal in the footwell, through a grommet in the bulkhead, and along the engine bay to the throttle linkage on the carburettors. The cable inner is connected to a balance bar that operates both carburettor throttle spindles simultaneously. Worn cables, perished outer sheaths and corroded linkage pivots all contribute to a sticky or notchy throttle response and should be addressed during routine servicing. The throttle pedal assembly itself is shared with the equivalent-period four-cylinder MGB GT, with the V8-specific element being the cable run and the carburettor-end linkage.
Choke Cable
The choke cable operates the cold-start enrichment levers on both carburettors via a cross-shaft. The choke knob on chrome-bumper V8s is the standard MGB pull-knob; rubber-bumper V8s use a T-shaped choke knob (introduced with the rubber-bumper specification across the MGB range). The choke cable runs from the dashboard through the bulkhead to the cross-shaft on the carburettors. As with the throttle cable, the inner cable can stretch and the outer sheath can deteriorate, leading to either an under-choking or stuck-choke condition.
Synchronisation
Correct synchronisation of the twin carburettors is essential for smooth idle and balanced fuelling. The throttle linkage includes adjustment provisions that allow the two carburettors to be balanced once the cables are correctly set. A carburettor balancing tool (carbalancer) measuring air flow through each carburettor is the appropriate tool for this work and is available in the Tools section.
MGOC Spares
MGOC Spares supplies throttle cables, choke cables, throttle linkage components, cable grommets, throttle pedal parts and chrome-bumper and rubber-bumper choke knobs for the MGB GT V8, see individual sub-sections for details.