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Chrysler LA 318 2-bbl specs: 318 ci (5.2L) 8-cylinder, 3.91 x 3.313 in (99.3 x 84.2 mm) bore and stroke. Rated 120-140 hp, 1975–1987.
The Chrysler LA 318 2-bbl is oversquare — the 3.91" bore exceeds the 3.313" stroke by 18.0% — a layout that favors airflow and RPM over leverage at the crank. The 3.313" stroke does not reach 4,000 ft/min of mean piston speed until about 7,250 RPM, so piston speed is not what limits this engine's revs — valvetrain and breathing are. A rod ratio of 1.848 is long by production standards — less side-load on the cylinder wall and gentler piston acceleration around TDC, the geometry that tolerates high RPM. Each of the 8 cylinders displaces 39.8 ci (651 cc).
It is one of 9 engines in the Chrysler 318ci family, all of them 318 ci — the differences between them are in compression, heads and rating, not displacement. 13 factory variants share these dimensions, rated from 120 to 140 hp across 1975–1987.
| Displacement | 318 ci / 5.2 L |
|---|---|
| Bore | 3.91" |
| Stroke | 3.313" |
| Cylinders | 8 |
| Configuration | V8 |
| Compression ratio | 8.5–9:1 (published figures vary) |
| Rod length | 6.123" |
| Rod ratio | 1.848 |
| Bore/stroke ratio | 1.18 |
| Block material | cast iron |
|---|---|
| Head material | cast iron |
| Valvetrain | OHV |
| Fuel type | gas |
| Firing order | 1-8-4-3-6-5-7-2 |
| Advertised HP | 120–140 hp |
| Years | 1975–1987 |
| Year | Version | HP @ rpm | Torque @ rpm | Comp. |
|---|---|---|---|---|
| 1980 | E45 net | 120 @ 3600 | 245 lb-ft @ 1600 | — |
| 1981 | net | 130 @ 4000 | 230 lb-ft @ 2000 | 8.5:1 |
| 1986 | net | 140 @ 3600 | 265 lb-ft @ 1600 | 9:1 |
Factory specification sheet.
| Bore/stroke character | 1.180 — oversquare — bore exceeds stroke, which favours higher RPM and larger valves |
|---|---|
| Mean piston speed at 6,000 RPM | 3,313 ft/min — conservative for a street engine |
| Rod ratio | 1.848 — long — less side loading on the cylinder wall, favours high RPM |
| Displacement per cylinder | 39.8 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 |
|---|---|---|
| 1975 | — | LA 318 2-bbl |
| 1976 | — | LA 318 2-bbl |
| 1979 | — | LA 318 2-bbl |
| 1980 | — | LA 318 2-bbl |
| 1980 | 120 hp | LA 318 2-bbl |
| 1981 | 130 hp | LA 318 2-bbl |
| 1982 | 130 hp | LA 318 2-bbl |
| 1983 | — | LA 318 2-bbl |
| 1983 | 130 hp | LA 318 2-bbl |
| 1984 | 130 hp | LA 318 2-bbl |
| 1985 | 140 hp | LA 318 2-bbl |
| 1986 | 140 hp | LA 318 2-bbl |
| 1987 | 140 hp | LA 318 2-bbl |
9 factory vehicles, 1968–1989. Each year opens that model's engine table.