The MGOC Spares range includes complete reconditioned engines for all three pushrod MGA variants, the 1489cc 1500, the 1588cc 1600, and the 1622cc Mk II. These engines are professionally remanufactured to exacting standards, delivering a unit that meets or exceeds the original factory specification. Each engine is stripped, cleaned, and inspected before rebuilding with a reground crankshaft, new main and big-end bearings, new pistons and rings to the correct bore size, a rebuilt cylinder head with new valves and guides, and renewed seals and gaskets throughout. All reconditioned units are supplied with lead-free-compatible cylinder heads to allow safe running on modern unleaded petrol.
Engine Prefix Identification
The engine prefix must be specified when ordering. The 1489cc 1500 engines carry the prefix 15GB (early cars) or 15GD (from chassis number 61504). The 1588cc 1600 engines carry prefix 16GA. The 1622cc Mk II engines carry prefix 16GC, available in two compression ratios: 8.9:1 high-compression (suffix H) and 8.3:1 low-compression (suffix L).
The distinction between 15GB and 15GD is particularly important, the 15GD's raised starter motor position means that a 15GB engine cannot be fitted to a later car without changing the gearbox mounting plate, gearbox tunnel, right-hand toeboard, and carpet. This makes it essential to match the engine prefix to the car's chassis specification.
Exchange Basis and Supply
Reconditioned engines are supplied on an exchange basis, with the customer's original engine returned as a rebuildable core. Engines are supplied less ancillaries, flywheel, starter motor, distributor, and manifolds are transferred from the outgoing unit and not included with the replacement. In some instances, where serviceable core units are in short supply, customers may be asked to provide their own unit for reconditioning rather than receiving an exchange from stock.
Stage II Performance Engines
For owners seeking improved power and torque, Stage II performance engines are available for all three pushrod variants. The Stage II specification is a comprehensive performance build, including a gas-flowed and ported cylinder head with improved valve seats and larger valves, a modified camshaft, vernier duplex timing gears for precise valve timing, a balanced rotating assembly (crankshaft, connecting rods, pistons, flywheel, and clutch), a dedicated engine backplate, and a choice of increased capacities over standard. The compression ratio is set to suit the intended fuel quality. Stage II engines are built to order, typically with a twelve-month unlimited-mileage guarantee, and should be specified in consultation with the technical team to ensure compatibility with the car's carburettor type, exhaust system, and cooling capacity.
Three-Bearing Crankshaft Considerations
All MGA pushrod engines use a three-bearing crankshaft. This arrangement is inherently less rigid than the later MGB's five-bearing design, making bottom-end balance particularly beneficial on performance builds. The three-bearing crank also means that main bearing wear has a more pronounced effect on oil pressure and engine smoothness than on a five-bearing engine. When assessing whether a rebuild or reconditioned exchange is the better option, the condition of the main bearing bores in the block is a critical factor, a block with worn main bearing bores beyond standard oversize limits will require line boring or replacement.
Ordering Notes
When ordering, provide the engine serial number prefix (stamped on a plate on the right-hand side of the block, just below the spark plugs between cylinders two and three), the car's chassis number, and whether the engine is for a standard restoration or a performance application. Pistons and bearings require the oversize to be stated if known. For engine rebuilds using individually sourced components rather than a complete reconditioned unit, a conversion gasket set is used alongside the head gasket set, with timing cover and rear crankshaft oil seals purchased separately.