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Chrysler 318ci (1978–1980) specs: 318 ci (5.2L) 8-cylinder, 3.91 x 3.313 in (99.3 x 84.2 mm) bore and stroke. Rated 135-150 hp, 1978–1980.
The Chrysler 318ci (1978–1980) 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 14 engines in the Chrysler 318ci family, all of them 318 ci — the differences between them are in compression, heads and rating, not displacement. 3 factory variants share these dimensions, rated from 135 to 150 hp across 1978–1980.
| Displacement | 318 ci / 5.2 L |
|---|---|
| Bore | 3.91" |
| Stroke | 3.313" |
| Cylinders | 8 |
| Configuration | V8 |
| 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 |
| Advertised HP | 135–150 hp |
| Years | 1978–1980 |
| 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 |
|---|---|---|
| 1978 | 150 hp | — |
| 1979 | 150 hp | — |
| 1980 | 135 hp | — |