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Subaru 61 specs: 1.0L (66.4 ci) 4-cylinder, 76 x 60 mm (2.9920 x 2.3620 in) bore and stroke, 9:1 compression. Rated 55 hp. OHV. Rod ratio and piston speed.
The Subaru EA (61) is oversquare — the 2.992" bore exceeds the 2.362" stroke by 26.7% — a layout that favors airflow and RPM over leverage at the crank. The 2.362" stroke does not reach 4,000 ft/min of mean piston speed until about 10,150 RPM, so piston speed is not what limits this engine's revs — valvetrain and breathing are. Each of the 4 cylinders displaces 16.6 ci (272 cc).
9:1 on aluminum heads is low by modern standards and generally happy on regular pump fuel.
It is one of 10 engines in the EA family, sitting between the 59.6 ci and 110 ci members. Factory fitments include the Subaru 1000, Subaru FF-1 Star.
| Displacement | 66.4 ci / 1 L |
|---|---|
| Bore | 2.992" |
| Stroke | 2.362" |
| Cylinders | 4 |
| Compression ratio | 9:1 |
| Bore/stroke ratio | 1.267 |
| Block material | aluminum |
|---|---|
| Head material | aluminum |
| Valvetrain | OHV |
| Fuel type | gas |
| Advertised HP | 55 hp |
| Bore/stroke character | 1.267 — oversquare — bore exceeds stroke, which favours higher RPM and larger valves |
|---|---|
| Mean piston speed at 6,000 RPM | 2,362 ft/min — conservative for a street engine |
| Displacement per cylinder | 16.6 ci |
| Static compression | 9:1 — low by modern standards, generally happy on regular pump fuel |
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