The MGA exhaust system runs along the left-hand side of the car, carrying spent gases from the left-mounted exhaust ports on the cylinder head rearwards through a single silencer to the tail pipe. Two fundamentally different exhaust arrangements were fitted during MGA production: a single-manifold, single-downpipe system used on all pushrod cars, 1500, 1600 and 1600 Mk II, and a twin-manifold, twin-downpipe system fitted exclusively to the Twin Cam, reflecting the different cylinder-head breathing and exhaust port layout of that engine. The two systems share no interchangeable components. Within each system, MGOC offers OE-pattern replacement components in mild steel and complete stainless-steel systems as an upgrade alternative, together with the manifold hardware, mountings, clamps and tail pipe accessories that complete an installation.
Pushrod exhaust system, 1500, 1600 and 1600 Mk II
All pushrod-engined MGAs use the same basic exhaust arrangement: a single three-branch cast iron manifold bolted to the left-hand side of the cylinder head, a single downpipe from the manifold flange, a front pipe running back along the left-hand side of the chassis, and a simple tubular silencer towards the rear with two mounting brackets, one in front of and one at the rear of the silencer. The system specification is common to all three pushrod variants, 1500, 1600 and 1600 Mk II, and the only factory deviation concerns late 1600 Mk II cars exported to Switzerland from car/chassis 108405, which carried an additional silencer in the front pipe to comply with Swiss noise legislation.
Cars built for the home or other export markets, of whatever pushrod variant, use the single-silencer system.
Twin Cam exhaust system
The Twin Cam exhaust is also on the left-hand side of the car but is more complex in construction. The Twin Cam cylinder head has its exhaust ports grouped to feed two exhaust manifolds rather than a single three-branch item, with two separate downpipes leading from the two manifolds. The front downpipe serves cylinders 1 and 4, the front and rear cylinders of the engine, while the rear downpipe serves cylinders 2 and 3, the two middle cylinders. The two downpipes merge into a single front pipe well forward of the silencer.
The Twin Cam silencer is similar in form to the pushrod unit but of a slightly different type, with a larger pipe diameter to match the twin-manifold system. No Twin Cam exhaust components, manifolds, downpipes, front pipe or silencer, are interchangeable with pushrod items.
Manifolds and fixings
The pushrod three-branch manifold is a cast-iron item finished as supplied in unpainted cast iron. The Twin Cam manifolds are likewise cast iron. Both installations use an engine-colour-finished heat shield between the inlet side of the carburettor installation and the adjacent exhaust hardware, the heat shield and its associated fixings sit within the Inlet Manifold & Heatshield node rather than here, but the exhaust manifold studs, brass nuts, manifold-to-head gaskets and downpipe flange hardware are all service items covered under Manifolds and Fixings for this section. On any exhaust work where the manifold is disturbed, the gaskets should be renewed rather than reused, as gasket material compresses permanently on first fitment.
Systems & Components versus Upgrades & Alternatives
Under Systems & Components, MGOC supplies OE-pattern mild-steel replacement systems (single-silencer pushrod and twin-manifold Twin Cam), together with the exhaust fixings and mountings that complete an installation, rubber hangers, bracket straps and the small hardware that secures the system to the chassis. Under Upgrades & Alternatives, stainless-steel exhaust systems are offered as a longer-life replacement for the original mild steel, manifold wrap and clamps are supplied for owners wanting to reduce engine-bay heat and carburettor heat-soak, and tail pipe accessories allow the exit to be dressed or finished differently from the original plain-cut tail.
OE-pattern versus stainless steel
OE-pattern mild-steel systems replicate the factory specification and are the correct choice for a concours restoration, where original materials and appearance matter. Mild steel is subject to internal and external corrosion, and the service life of a mild-steel system in UK use is typically several years before re-replacement is needed. Stainless-steel systems eliminate corrosion as a failure mode and carry a materially longer service life, at the cost of a slight variation in exhaust note compared with the original mild-steel item and a mirror-finish silencer appearance rather than the plain matt-black finish of a factory-pattern system.