REFERENCE DESK / 1975 MG MIDGET 1500
The 3D pieces are original interpretations of factory layouts and exploded parts drawings. These are the source plates used to decide which assemblies belong in the car, how they connect, and which details vary by model year.
The catalog and workshop drawings establish component relationships and service names. They do not provide a complete set of measurable surfaces for an exact 3D reconstruction. The shape of any part should be checked against the physical car before repair or ordering.
The scanned first part covers specifications and maintenance. Its underside layout on PDF page 29 places the engine, gearbox, propeller shaft, live axle, steering and suspension in relation to one another. The specification pages give a 2.03 m wheelbase and 3.60 m overall length.
Open workshop layout, PDF p. 29 ↗Exploded plates show the 1500 engine, cooling, carburetion, gearbox, suspension, body panels and trim. The drawings guide assembly groupings and the individual-part links in the model.
Open full catalog ↗The 1975 1500 begins at GAN6-154101 and uses the FP engine prefix. These are model-range identifiers; the car’s chassis and engine plates are needed for exact specification.
Open production history ↗A four-view 1975 roadster drawing was used as a visual cross-check for the exterior silhouette. The model itself contains new geometry and does not reproduce that drawing.
View drawing source ↗Explore and download the measured-core STEP assembly ↗
Your existing engine-bay photos (especially IMG_6797, IMG_6853 and IMG_6856) show the red rocker cover clearly enough to use a matching replacement gasket as a scale anchor. AJUSA 11007400, cross-referenced to AJM414, is listed at 360 × 110 mm ↗. The CAD study now uses that footprint for the cover; its height and stamped contours remain provisional. A listed 58 mm oil-filler cap ↗ is only a secondary check because the photographed cap has a different finish.
The Midget 1500 uses the Triumph Spitfire 1500 engine family. The factory Midget manual identifies it as PE94J, with four cylinders and 1,493 cm³ displacement. The shared core makes Triumph drawings useful, but the Midget catalog warns that its FP engine and the Spitfire FM engine differ in fuel pump, distributor and some other fittings. First confirm the engine prefix on this car before fixing a variant in CAD.
| Factory datum | Value | CAD use |
|---|---|---|
| Cylinder bore | 73.7 mm | Four cylinder volumes and piston envelope |
| Crankshaft stroke | 87.5 mm | Crank throw radius: 43.75 mm |
| Connecting rod centers | 145.90–146.10 mm | Piston and crank kinematics |
| Crank main journals | 58.713–58.725 mm diameter | Bearing interfaces |
| Crankpin journals | 47.625–47.638 mm diameter | Connecting rod big ends |
| Gudgeon pin | 20.63–20.64 mm diameter | Piston and rod small ends |
| Inlet valve head | 34.97–35.01 mm diameter | Cylinder head valve envelope |
| Exhaust valve head | 29.66–29.76 mm diameter | Cylinder head valve envelope |
These dimensions come from factory general specifications, PDF pp. 11–12 ↗. The additional workshop-manual scan, part 3 ↗ shows crankshaft, cylinder block, head, rocker gear and engine mounting procedures in more detail. The factory Spitfire 1500 parts catalog, RTC9819CB ↗ adds exploded block, sump and cylinder-head plates beginning on PDF page 30. Its Spitfire part numbers require a Midget fitment check before use. Download the measured-data JSON ↗
Still needed for an accurate solid model: cylinder-center spacing; block, head and sump exterior dimensions; face and bolt-hole coordinates; intake and exhaust port geometry; mounting points; and verified 1975 North American carburetor and emissions hardware on this car. The available service plates establish construction and many machined diameters, but they are not scaled manufacturing drawings. Those remaining shapes need dimensioned parts, direct measurement, or a scan. The linked measured-core assembly marks provisional shapes and provides an editable STEP file for the next measurement pass.
| Assembly | Moss PDF page | What it informs |
|---|---|---|
| 1500 external engine | 32 ↗ | Block, front cover, water pump and mounting relationships. |
| Internal engine | 33 ↗ | Four pistons, connecting rods, crankshaft, timing chain and flywheel. |
| Cylinder head | 34 ↗ | Valve train, rocker shaft, head and rocker cover. |
| Cooling system | 37 ↗ | Radiator, fan, pump, hoses and year-specific cooling notes. |
| Carburetor and manifolds | 42 ↗ · 47 ↗ | Zenith-Stromberg assembly and intake/exhaust routing. The catalog lists Federal and California variants separately. |
| Clutch and gearbox | 52 ↗ · 58 ↗ | Engine-to-gearbox sequence and 1500 gearbox internals. |
| Axle and suspension | 59 ↗ · 62 ↗ · 64 ↗ | Live rear axle, front wishbone/coil layout and rear leaf springs. |
| Body and trim | 71 ↗ · 72 ↗ · 84 ↗ | Separate panels, inner shell structure and rubber bumpers. |
Your engine-bay photographs establish the car’s visible olive paint, red-orange rocker cover, orange ignition leads, pale fan, and intake arrangement. They do not by themselves prove that every component is factory original. The viewer links selected parts to those photographs.
The 3D meshes, separation paths and hidden internal surfaces remain approximations. I have avoided assigning exact catalog part numbers where the chassis and engine plates have not been inspected.