See other engines in this family
MG 18G / 18GA / 18GB specs: 110 ci 4-cylinder, 80.3 x 88.9 mm (3.1600 x 3.5000 in) bore and stroke, 8.8:1 compression. Built 1963–1967. Used in the MG MGB.
The MG 18G / 18GA / 18GB is undersquare — the 3.5" stroke exceeds the 3.16" bore by 9.7% — a layout that trades peak RPM for leverage and torque low in the range. The 3.5" stroke puts mean piston speed at 4,000 ft/min around 6,850 RPM, which is where a production bottom end is generally considered at its limit. Each of the 4 cylinders displaces 27.5 ci (451 cc).
8.8:1 is low by modern standards and generally happy on regular pump fuel.
It is one of 3 engines in the MG 110ci family, all of them 110 ci — the differences between them are in compression, heads and rating, not displacement. 5 factory variants share these dimensions across 1963–1967.
| Displacement | 110 ci |
|---|---|
| Bore | 3.16" |
| Stroke | 3.5" |
| Cylinders | 4 |
| Configuration | I4 |
| Compression ratio | 8.8:1 |
| Bore/stroke ratio | 0.903 |
| Fuel type | gas |
|---|---|
| Years | 1963–1967 |
| Bore/stroke character | 0.903 — undersquare — stroke exceeds bore, which favours low-end torque |
|---|---|
| Mean piston speed at 6,000 RPM | 3,500 ft/min — conservative for a street engine |
| Displacement per cylinder | 27.5 ci |
| Static compression | 8.8:1 — low by modern standards, generally happy on regular pump fuel |
Each link opens the calculator with this engine's specs already filled in.
These records share identical bore, stroke, displacement and compression. They differ by model year and factory power rating.
| Year | Advertised HP | Code |
|---|---|---|
| 1963 | — | 18G / 18GA / 18GB |
| 1964 | — | 18G / 18GA / 18GB |
| 1965 | — | 18G / 18GA / 18GB |
| 1966 | — | 18G / 18GA / 18GB |
| 1967 | — | 18G / 18GA / 18GB |
1 factory vehicle, 1963–1967. Each year opens that model's engine table.