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Chevrolet 307ci specs: 307 ci (5.0L) 8-cylinder, 3.875 x 3.25 in (98.4 x 82.6 mm) bore and stroke, 9.651:1 compression. Rated 115-130 hp, 1972–1973.
The Chevrolet 307ci is oversquare — the 3.875" bore exceeds the 3.25" stroke by 19.2% — a layout that favors airflow and RPM over leverage at the crank. The 3.25" stroke does not reach 4,000 ft/min of mean piston speed until about 7,400 RPM, so piston speed is not what limits this engine's revs — valvetrain and breathing are. A rod ratio of 1.754 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 38.4 ci (629 cc).
9.651:1 on iron heads is in the range that usually runs on pump premium; iron holds heat, so treat it as the less forgiving side of that range.
It is one of 4 engines in the Chevrolet 307ci family, all of them 307 ci — the differences between them are in compression, heads and rating, not displacement. 2 factory variants share these dimensions, rated from 115 to 130 hp across 1972–1973.
| Displacement | 307 ci / 5 L |
|---|---|
| Bore | 3.875" |
| Stroke | 3.25" |
| Cylinders | 8 |
| Configuration | V8 |
| Compression ratio | 9.651:1 |
| Rod length | 5.7" |
| Rod ratio | 1.754 |
| Bore/stroke ratio | 1.192 |
| Piston deck clearance | 0.002" |
| Block material | cast iron |
|---|---|
| Head material | cast iron |
| Valvetrain | OHV |
| Fuel type | gas |
| Advertised HP | 115–130 hp |
| Years | 1972–1973 |
| Bore/stroke character | 1.192 — oversquare — bore exceeds stroke, which favours higher RPM and larger valves |
|---|---|
| Mean piston speed at 6,000 RPM | 3,250 ft/min — conservative for a street engine |
| Rod ratio | 1.754 — long — less side loading on the cylinder wall, favours high RPM |
| Displacement per cylinder | 38.4 ci |
| Static compression | 9.651:1 — in the range that usually runs on pump premium |
| Intake valve diameter | 1.725" |
|---|---|
| Exhaust valve diameter | 1.505" |
| Chamber volume | 65.5 cc |
| Rocker ratio | 1.5:1 |
| Lifter type | hydraulic |
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 |
|---|---|---|
| 1972 | 130 hp | — |
| 1973 | 115 hp | — |