Pontiac 305ci specs: 3.736 x 3.484 in (94.9 x 88.5 mm) bore and stroke, shared by all 14 versions. Displacement, compression and factory ratings.
| Displacement | 305 ci |
|---|---|
| Cylinders | 8 |
| Bore | 3.736" |
| Stroke | 3.484" |
| Compression | 9.2–11.4:1 |
| Advertised power | 125–230 hp |
| Years | 1977–1992 |
| Cylinder head data | 7 of 14 engines |
| Engine | Displacement | Bore × Stroke | CR | HP |
|---|---|---|---|---|
| Pontiac 305ci (1977) · 145 hp | 305 ci | 3.736" × 3.484" | 9.241:1 | 145 |
| Pontiac 305ci (1985) · 155 hp | 305 ci | 3.736" × 3.484" | 9.901:1 | 155 |
| Pontiac 305ci · 3.736" × 3.484" · 11.051:1 | 305 ci | 3.736" × 3.484" | 11.051:1 | 150–190 |
| Pontiac 305ci (1986) · 210 hp | 305 ci | 3.736" × 3.484" | 11.1:1 | 210 |
| Pontiac 305ci · 3.736" × 3.484" · 11.38:1 | 305 ci | 3.736" × 3.484" | 11.38:1 | 170 |
| Pontiac 305ci · 3.736" × 3.484" · 10.49:1 | 305 ci | 3.736" × 3.484" | 10.49:1 | 190–220 |
| Pontiac 305ci · 3.736" × 3.484" · 10.35:1 | 305 ci | 3.736" × 3.484" | 10.35:1 | 205–230 |
| LG3 | 305 ci | 3.736" × 3.484" | — | 125–145 |
| LG4 | 305 ci | 3.736" × 3.484" | — | 145–170 |
| LU5 | 305 ci | 3.736" × 3.484" | — | 165–175 |
| L69 | 305 ci | 3.736" × 3.484" | — | 190 |
| LB9 | 305 ci | 3.736" × 3.484" | — | 190–230 |
| L03 | 305 ci | 3.736" × 3.484" | — | 170 |
| LG4 / LG3 | 305 ci | 3.736" × 3.484" | — | 155 |
Compression spans 9.241:1 to 11.38:1, 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.