This section covers original equipment specification mild steel exhaust systems and their individual components, together with the cast iron exhaust manifolds and associated fixings.
OE Mild Steel Systems
The MGB exhaust system comprises twin downpipes from the cast iron manifold, joining ahead of a centre silencer, then a rear interpipe leading to the rear silencer and tailpipe, which exits on the left-hand side of the car. This layout remained fundamentally unchanged across production from 1962 to 1980, though the centre silencer changed from a flattened oval section on chrome bumper cars to a crimped box type from the start of rubber bumper production in 1974. The rear silencer was always a cylindrical type.
Throughout production, further changes were made to improve system longevity and reduce noise, a twin perforated tube front silencer was introduced in July 1963, double end plate silencers from March 1966, improved material specification in 1968, a stainless steel tailpipe from October 1969, and a three-pass front silencer from September 1977 to meet EEC noise regulations of a maximum 82dB. One-piece mild steel systems are available for both chrome bumper and rubber bumper cars, providing a complete replacement from downpipe to tailpipe.
For owners who only need to replace a single worn section, the individual components, downpipe, front interpipe, centre silencer, rear interpipe, and rear silencer, are also available separately. The front interpipe is common to both chrome bumper and rubber bumper applications. The improved Club exhaust is a one-piece mild steel system designed to fit both chrome and rubber bumper cars. Built from 18-gauge heavy duty steel for extra strength and durability, it features a bomb-style centre box of heavy duty design and a rear box incorporating twin walls, skid plates, and dense fibre insulation packing.
It carries a 15-month guarantee, offering a longer service life than standard-gauge mild steel systems.
Cast Iron Manifolds
Two types of cast iron exhaust manifold were fitted across production. Early 18G-series engines (1962 to 1971) used a thick-flange manifold, while 18V-series engines from 1971 onwards were fitted with a thin-flange manifold which incorporated a hot-spot facility for the carburettors. The stud configuration also differs, the thick-flange type uses two outer studs and four inner studs of differing lengths, whereas the thin-flange type uses six identical studs. Reconditioned manifolds are available for both types, and the correct manifold gasket should always be renewed when refitting.
Brass nuts are recommended for the manifold-to-head fixings, as they resist seizing onto the studs after repeated heat cycles. Long-reach brass nuts are also available as an alternative, making access easier in the confined space between the manifold and the cylinder head. Downpipe seals, downpipe studs, and 1?-inch U-clamps complete the range of OE fixings.
When fitting a new system, it is advisable to renew all gaskets, seals, and corroded fixings at the same time. For complete mounting hardware, brackets, rubber bobbins, and all associated clamps and fasteners, exhaust fitting kits tailored for each system type are listed in the Exhaust Fitting Kits section.