The MGB GT V8 was fitted with twin SU HIF6 carburettors, Horizontal Integral Float, 1.75 inch (44.5mm) throat size. These are larger than the HIF4 carburettors fitted to the four-cylinder MGB and were chosen to provide the air capacity needed by the V8 engine. The carburettors are a matched pair, mounted on the two-piece inlet manifold at the rear of the engine, with a balanced throttle linkage and a synchronised cold-start cross-shaft.
Carburettor Operation
Each carburettor uses a variable-venturi (constant-depression) principle, a piston rises in the carburettor body as engine demand increases, increasing the venturi area and drawing fuel through a tapered needle in a fixed jet. The float chamber maintains constant fuel level via a needle valve and float, and the integral float arrangement of the HIF type tucks the float chamber under the carburettor body for compact packaging. Cold-start enrichment is provided by a separate jet that adds fuel to the mixture when the choke is operated.
Carburettor Components
Internal components include the dashpot piston and damper, suction chamber, needle, jet, float and float needle valve, throttle spindle and butterfly, and the various seals and gaskets. Most can be renewed individually as part of a routine service or rebuild. The specific needle profile fitted to the V8 carburettors is matched to the engine's fuelling requirement and should not be substituted with other patterns without adjusting the rest of the fuelling specification.
Sub-Sections
Carburettor Linkages and Components covers throttle linkage parts, choke cross-shaft components and external fittings. Carburettor Service and Rebuild Kits covers service kits with all routine consumables. Carburettor Needles and Jets covers individual needle and jet specifications.
MGOC Spares
MGOC Spares supplies SU HIF6 carburettors, service and rebuild kits, individual needles and jets, linkage components and all associated parts for the MGB GT V8, see individual sub-sections for details.