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Honda EF1 specs: 1.6L (97.6 ci) 4-cylinder, 74 x 93 mm (2.9134 x 3.6614 in) bore and stroke, 8:1 compression. Rated 68 hp, 1976–1978.
The Honda E-series (EF1) is undersquare — the 3.6614" stroke exceeds the 2.9134" bore by 20.4% — a layout that trades peak RPM for leverage and torque low in the range. The 3.6614" stroke puts mean piston speed at 4,000 ft/min around 6,550 RPM, which is where a production bottom end is generally considered at its limit. Each of the 4 cylinders displaces 24.4 ci (400 cc).
8:1 is low by modern standards and generally happy on regular pump fuel.
It is one of 10 engines in the E-series family, the largest at 97.6 ci. 3 factory variants share these dimensions, rated at 68 hp across 1976–1978.
| Displacement | 97.6 ci / 1.6 L |
|---|---|
| Bore | 2.9134" |
| Stroke | 3.6614" |
| Cylinders | 4 |
| Configuration | I4 |
| Compression ratio | 8:1 * |
| Bore/stroke ratio | 0.796 |
* Compression ratio from a single source; not yet cross-verified.
| Valvetrain | SOHC |
|---|---|
| Fuel type | gas |
| Advertised HP | 68 hp |
| Years | 1976–1978 |
| Year | Version | HP @ rpm | Torque @ rpm | Comp. |
|---|---|---|---|---|
| 1976 | EF1 net | 68 | — | — |
| 1977 | EF1 net | 68 | — | — |
| 1978 | EF1 net | 68 | — | — |
Factory specification sheet.
| Bore/stroke character | 0.796 — undersquare — stroke exceeds bore, which favours low-end torque |
|---|---|
| Mean piston speed at 6,000 RPM | 3,661 ft/min — in the range typical of performance street engines |
| Displacement per cylinder | 24.4 ci |
| Static compression | 8:1 — low by modern standards, generally happy on regular pump fuel |
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 |
|---|---|---|
| 1976 | 68 hp | EF1 |
| 1977 | 68 hp | EF1 |
| 1978 | 68 hp | EF1 |
1 factory vehicle, 1976–1978. Each year opens that model's engine table.