Bore, stroke, displacement and compression for all 4 Toyota R engines, compared side by side. Plus rod ratio and head specs where published.
| Displacement | 120.1–133.6 ci |
|---|---|
| Cylinders | 4 |
| Bore | 3.484" |
| Stroke | 3.150–3.504" |
| Advertised power | 90–108 hp |
| Years | 1972–1980 |
| Engine | Displacement | Bore × Stroke | CR | HP |
|---|---|---|---|---|
| 20R | 133.6 ci | 3.4843" × 3.5039" | — | — |
| 20R | 133.6 ci | 3.4843" × 3.5039" | — | 90 |
| 18R-C | 120.1 ci | 3.4843" × 3.1496" | — | — |
| 18R-C | 120.1 ci | 3.4843" × 3.1496" | — | 108 |
Every engine here shares a 3.4843" bore; displacement varies by stroke alone, which is the signature of a family built on one block with different cranks.
2 of 4 are oversquare — bore larger than stroke, which favours revs over low-end torque.
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.