Bore, stroke, displacement and compression for all 3 Mitsubishi Astron engines, compared side by side. Plus rod ratio and head specs where published.
| Displacement | 151–156 ci |
|---|---|
| Cylinders | 4 |
| Bore | 3.587" |
| Stroke | 3.740–3.858" |
| Compression | 8.2–21.0:1 |
| Advertised power | 74–114 hp |
| Years | 1978–1983 |
| Engine | Displacement | Bore × Stroke | CR | HP |
|---|---|---|---|---|
| 4G54 | 156 ci | 3.5866" × 3.8583" | 8.2:1 | 114 |
| 4G54 | 156 ci | 3.5866" × 3.8583" | — | 105 |
| 4D56 | 151 ci | 3.5866" × 3.7402" | 21:1 | 74 |
Every engine here shares a 3.5866" bore; displacement varies by stroke alone, which is the signature of a family built on one block with different cranks.
Compression spans 8.2:1 to 21:1, so fuel requirements differ meaningfully between members — worth checking before assuming parts interchange.
2 of 3 are undersquare — stroke larger than bore, favouring torque low in the range.
Each engine page carries rod ratio, mean piston speed, bore/stroke character and cylinder head specs where published, and links into the calculators with its dimensions already filled in.