The MGB GT V8 was fitted at the factory with cast-iron exhaust manifolds, one for each cylinder bank. Each manifold collects gases from its four cylinders and routes them rearwards to exit at the rear of the head, where the manifold joins a single downpipe per side. The cast-iron construction provides good thermal mass and noise damping at the cost of some additional weight and back-pressure compared with tubular alternatives.
Manifold Gaskets
Each manifold is sealed to the cylinder head face with a high-temperature gasket. The gaskets seal eight ports in total, four per side, and should be renewed whenever the manifolds are removed for any reason. Re-using old manifold gaskets is a common cause of exhaust leaks shortly after engine work, as the gaskets compress permanently in service and lose their sealing capability.
Heat Shields
Heat shields fitted between the exhaust manifolds and adjacent components manage radiated heat to protect the carburettors, spark plug leads and other heat-sensitive items. Heat shields were added to the factory specification at production stages V8 1956 (September 1974, four middle plug leads) and V8 2266 (February 1975, two front plug leads). Cars before these chassis numbers can have the heat shields fitted retrospectively as good practice.
Studs and Nuts
Each manifold is secured to the cylinder head with studs threaded into the head and nuts and washers on the manifold side. The studs and nuts run hot in service and should be inspected for thread condition during any manifold work. Brass nuts are typically used in this position as they are less prone to seizing on hot threads than steel.
MGOC Spares
MGOC Spares supplies cast-iron V8 exhaust manifolds, manifold gaskets, heat shields, studs, nuts and all associated fixings for the MGB GT V8.