Pontiac 138ci specs: 3.625 x 3.35 in (92.1 x 85.1 mm) bore and stroke, shared by all 5 versions. Displacement, compression and factory ratings.
| Displacement | 138 ci |
|---|---|
| Cylinders | 4 |
| Bore | 3.625" |
| Stroke | 3.350" |
| Compression | 9.5–11.9:1 |
| Advertised power | 115–180 hp |
| Years | 1988–1994 |
| Engine | Displacement | Bore × Stroke | CR | HP |
|---|---|---|---|---|
| Pontiac 138ci (1988) · 150 hp | 138 ci | 3.625" × 3.35" | 10.45:1 | 150 |
| Pontiac 138ci (1989) · 150 hp | 138 ci | 3.625" × 3.35" | 11:1 | 150 |
| Pontiac 138ci (1992) · 120 hp | 138 ci | 3.625" × 3.35" | 9.5:1 | 120 |
| Pontiac 138ci · 3.625" × 3.350" · 11.9:1 | 138 ci | 3.625" × 3.35" | 11.9:1 | 160–180 |
| L40 | 138 ci | 3.625" × 3.35" | — | 115 |
Compression spans 9.5:1 to 11.9:1, so fuel requirements differ meaningfully between members — worth checking before assuming parts interchange.
All 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.