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MG 18GK / 18V specs: 110 ci 4-cylinder, 80.3 x 88.9 mm (3.1600 x 3.5000 in) bore and stroke. Built 1968–1974. Used in the MG MGB. Rod ratio and piston speed.
The MG 18GK / 18V 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).
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. 7 factory variants share these dimensions across 1968–1974.
| Displacement | 110 ci |
|---|---|
| Bore | 3.16" |
| Stroke | 3.5" |
| Cylinders | 4 |
| Configuration | I4 |
| Compression ratio | 8–9:1 (published figures vary) |
| Bore/stroke ratio | 0.903 |
| Fuel type | gas |
|---|---|
| Years | 1968–1974 |
| 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 |
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 |
|---|---|---|
| 1968 | — | 18GK / 18V |
| 1969 | — | 18GK / 18V |
| 1970 | — | 18GK / 18V |
| 1971 | — | 18GK / 18V |
| 1972 | — | 18GK / 18V |
| 1973 | — | 18GK / 18V |
| 1974 | — | 18GK / 18V |
1 factory vehicle, 1968–1980. Each year opens that model's engine table.