The MGC rocker cover is a distinctive pressed-steel component secured to the cylinder head by seven screws with plain washers. The rocker cover gasket, a cork or composite seal, should be replaced whenever the cover is removed to prevent oil leakage. An oil filler cap is fitted centrally to the top of the rocker cover. On non-USA, non-Canadian cars, two self-adhesive labels were fitted: an MG badge label at the front and a Weslake patent label at the rear, both aligned to be read from the left-hand side of the engine bay.
USA and Canadian cars carried an emissions label in place of the MG badge, identifying the emissions control specification of the engine.
Crankcase Breathing Systems
The crankcase breathing system changed at the 1969 model year, and identifying which system is fitted to your car is essential when ordering replacement components. Cars up to engine numbers 29G/3200 and 29GA/1400 were fitted with a positive crankcase ventilation (PCV) valve, mounted on a bracket and connected by hoses with clips to the crankcase and inlet manifold. The PCV valve is a serviceable item, a service kit, individual plunger, diaphragm, cover, spring, and associated hardware are all available for rebuilding. The cover changed at the same engine number breakpoint, so the correct cover must be specified when ordering.
From engine numbers 29G/3201, 29GA/1401, and 29GB/101 onwards, the PCV valve was replaced by a carburettor crankcase ventilation system. This uses a Y-piece connected by hoses to both carburettors, drawing crankcase vapours into the inlet airstream via the carburettor air intakes. Hoses are sold by the metre, with appropriate clips. A K&N engine breather filter is available as an alternative to either closed-circuit system for owners who wish to run an open breather, venting filtered crankcase vapours directly to atmosphere.
Side Covers
The C-series engine block has three side covers (front, centre, and rear) that provide access to the camshaft followers and internal components. The front side cover uses a dedicated gasket with five screws and sealing washers. The centre and rear side covers share a common gasket design, with two different fixing methods used during production: the original method using screws with O-rings, and an alternative method using a screw, cup washer, and rubber oil seal. A centre cover panel is available for replacement.
These side covers should be checked for oil leakage during any engine inspection, the gaskets and O-rings deteriorate over time and are a common source of oil weeping on the C-series engine.
Emissions Equipment, North American Cars
On USA and Canadian market MGCs, the emissions control equipment was far more extensive than on home market cars. In addition to the PCV or carburettor crankcase ventilation system, North American cars were fitted with air injection equipment including an air pump, manifold, gulp valve, check valve, and associated plumbing. A temperature-controlled carburettor float chamber cooling system, a small blower motor ducting cool air to the float chambers, was also unique to North American specification cars. Very little of this additional equipment remains available; owners requiring air injection or float chamber cooling components should contact MGOC Spares, who will strive to source items where possible.