The MGB GT V8 fuel system is significantly different from the four-cylinder MGB. Two SU HIF6 carburettors are mounted at the rear of the engine on a two-piece inlet manifold, with a separate cold-start enrichment cross-shaft and balanced throttle linkage. An SU high-pressure electric fuel pump, mounted behind the heelboard on the right-hand side of the car (the same pump fitted to MGB and MGC), delivers petrol from the steel fuel tank to the carburettors. The air filter housing is V8-specific, sized to suit the rear-mounted twin carburettors and the under-bonnet packaging.
Fuel lines, breather system and inlet manifold are all V8-specific items not interchangeable with the four-cylinder MGB.
Twin SU HIF6 Carburettors
The V8 uses two SU HIF6 carburettors, larger than the HIF4 carburettors fitted to the four-cylinder MGB. The HIF6 designation indicates Horizontal Integral Float, 6 standing for the 1.75 inch (44.5mm) throat size. Both carburettors operate together via a balanced throttle linkage, with synchronised choke operation through a cross-shaft. The cold-start enrichment is choke-cable operated rather than electric. Correct synchronisation of the two carburettors is essential for smooth idle and balanced fuelling.
Two-Piece Inlet Manifold
The V8 inlet manifold is a two-piece arrangement: a Rover penthouse-style base sits in the V between the cylinder heads, with a V-shaped MG-specific adaptor on top to mount the twin SU carburettors at the rear of the engine. The rearward carburettor mounting is a key feature of the MGB GT V8 installation, it allowed MG to fit the V8 within the standard MGB engine bay without a bonnet bulge, by tucking the carburettors into the available space above the bellhousing.
Fuel Tank and Pump
The fuel tank is mounted at the rear of the car, with a sender unit reading fuel level for the dashboard gauge. The factory fuel pump is the SU AUF 305 electric pump (the modern AZX1307 is the available equivalent replacement, fully interchangeable with the AUF 305), mounted behind the heelboard on the right-hand side of the car. Fuel is drawn from the tank through a steel pipe and pushed under pressure through pipework along the chassis, through a fuel filter, and to the carburettors. The pump and tank arrangement is essentially shared with the contemporary MGB and MGC.
Sub-Sections
Air Filters and Housings, Fuel Pumps and Fixings, Breather System, Carburettor and Components, Fuel Lines, Fuel Tanks Fillers and Sender Units, and Inlet Manifold and Heatshield each cover their respective subsystems. Upgrades and Alternatives covers performance air filters, performance carburettors, fuel regulators and uprated fuel pumps.
MGOC Spares
MGOC Spares supplies the full range of MGB GT V8 fuel system components, see individual sub-sections for details.