The MGB fuel system routes fuel from the rear-mounted tank, via an electrical pump behind the heelboard on the right-hand side of the ca, through a main feed pipe running along the underside of the car, and into the engine bay where it splits to supply the twin carburettors. The engine bay fuel line arrangement changed several times during production, and the hose layout, connections, and clips differ depending on which carburettor type is fitted and whether the car is a chrome bumper or rubber bumper model. Three main configurations exist.
Cars with HS4 carburettors from 1962 to 1972 use a feed arrangement incorporating a T-piece which splits the fuel supply between the front and rear carburettors, connected by Petroflex braided hoses with dedicated clips. Cars with HIF4 carburettors from 1972 to September 1976 use a revised layout with a disposable in-line fuel filter and different hose routing to suit the HIF4’s integral float chamber.
From September 1976 onwards, further changes were made to the fuel pipe connections in line with the redesigned fuel tank and filler arrangement introduced at that point.
Fuel Line Kits
Complete fuel line kits are available for each of these three configurations, containing the correct copper pipes, hoses, and clips for the specific application. These kits use malleable copper piping that can be shaped neatly by hand for a professional finish, and which will not corrode in the way that the original steel pipework does over time. Each kit includes a special nut driver for the clips. The main copper feed pipe running along the underside of the car from the boot to the engine bay is available separately and is common to most applications.
The tank-to-pump pipework and connections differ between early chrome bumper cars (up to 1964), later chrome bumper cars (1964 to 1974), early rubber bumper cars (1974 to September 1976), and late rubber bumper cars (September 1976 onwards), reflecting changes to the pump connection type and tank sender arrangement. Engine bay Petroflex braided hose kits are available as a set for each carburettor configuration, bundling the correct hose lengths and clips for the T-piece to carburettor runs on HS4 cars, or the filter to carburettor runs on HIF4 cars. Individual hose lengths are also sold separately for owners replacing a single deteriorated section. Rubber fuel hose is available by the metre for general-purpose replacement work.
Carburettor overflow pipes and their associated clips and brackets are also covered in this section, and these too differ across production, the arrangement changed between 1962 to 1968, 1968 to 1974, and rubber bumper cars, with the clips and brackets varying accordingly.
Fuel Filters & Hoses
A fuel filter should always be present in the engine bay fuel line. The standard disposable plastic filter is a simple and effective safeguard against dirt and debris reaching the carburettor needle valves, where contamination can cause sticking and erratic running. Chrome and toughened glass filters are available as a higher-quality alternative, offered in two union sizes to suit different pipe diameters, with replacement filter elements also available. Petroflex braided fuel hose is available in a range of pre-cut lengths as well as by the metre, and makes an attractive and durable upgrade over the original rubber hose, particularly in a rubber bumper engine bay where the standard hoses are more visible.
End caps are available for capping off unused hose ends where the fuel system has been modified.