The MGC is fitted with twin SU HS6 carburettors throughout production, the same basic type as the MGB but in the larger 1¾-inch choke diameter suited to the six-cylinder engine's greater airflow requirements. Four different carburettor specifications were used across the MGC's two-year production run, determined by market and model year. The specification number is sometimes found stamped on a small identification tag attached to the float chamber lid, and is the most important reference when ordering carburettor parts, needles, jets, jet bearings, choke cam levers, and pick-up lever assemblies all differ between specifications.
Carburettor Specifications
For 1967 to 1968 home market and most export cars with 29G engines (and 29GB French-market engines), the specification was AUD150, using a fixed ST needle as standard with C1W (weak) and SQ (rich) alternatives. North American 29GA cars for the 1968 model year used AUD287 with a fixed KM needle. From the 1969 model year, engine numbers 29G/3201 and 29GA/1401 onwards, the specification changed to AUD341 for non-North American cars, retaining the same needle options as AUD150, and to AUD342 for North American cars, which introduced spring-loaded biased needles of type BAD. The change to biased needles on the AUD342 was significant, the spring-loaded needle is self-centring within the jet, compensating for minor misalignment and reducing wear.
Fuel Tank and Pump, Shared with MGB
The MGC shares its fuel tank and fuel pump with the contemporary MGB (1967 to 1969 specification). The fuel tank is the larger bolt-on type of approximately 58 litres capacity. The SU electric fuel pump is mounted behind the heelboard on the right-hand side of the car and delivers fuel at low pressure to the twin carburettors via the fuel line system. A blanking plate with gasket seals the unused mechanical fuel pump aperture on the engine block, a casting feature inherited from the C-series engine's Austin-Healey ancestry that was never used on the MGC.
Fuel Lines, MGC-Specific
The fuel line routing from tank to carburettors is MGC-specific, owing to the different engine bay layout created by the six-cylinder installation and the forward-mounted radiator. A complete copper fuel pipe kit is available covering all fuel pipes with fixings. The fuel delivery route runs from the tank pipe through Petroflex flexible hose sections to the pump pipe, then via the main feed pipes to a T-piece that splits the supply to the two carburettors. Overflow pipes and breather tubing complete the fuel system plumbing.
Inlet Manifold, Two Types
Two different inlet manifolds were used: one for 29G and 29GB engines and one for 29GA engines, which incorporates additional emissions control provisions. Both are available on an exchange basis. The inlet manifold incorporates a hot-spot connection to the exhaust manifold, with a heatshield fitted above to protect the carburettors from radiant heat.