The factory twin SU HIF6 carburettors are well-matched to the standard 3528cc engine. For engines built to higher power levels, capacity-upgrade engines, modified standard engines with performance heads and cams, the standard carburettors can become a flow restriction at peak power. Performance carburettor options provide additional air capacity to suit these higher-output engines.
Uprated SU Components
Within the standard SU HIF6 framework, alternative needle profiles, jet sizes and metering components allow the carburettors to be tailored to a modified engine specification. This is typically the first level of carburettor work, re-needling and re-jetting the standard carburettors to suit the modified engine's fuelling requirement, without changing the carburettor type itself.
Larger Carburettors
Larger SU carburettors than the HIF6, for example HS8 or larger HIF instruments, are available where the engine specification requires more flow than the HIF6 can provide. Fitting larger carburettors usually requires manifold modification or a dedicated aftermarket inlet manifold, since the carburettor mounting flanges differ.
This is a substantial change and should be undertaken as part of a complete engine specification.
Specification Matching
Performance carburettor selection should always be done as part of a coherent engine specification. Mismatched carburettor sizing can produce poor running, peaky power delivery, or rich-running at part throttle that wastes fuel and risks bore wash. The parts team can advise on appropriate carburettor specification matched to the rest of the engine build.
MGOC Spares
MGOC Spares supplies uprated SU carburettor components and performance carburettor options for the MGB GT V8, engineering staff are available to discuss specification.