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Ford 138ci specs: 138 ci (2.3L) 4-cylinder, 3.444 x 3.70 in (87.5 x 94 mm) bore and stroke, 9.4:1 compression. Rated 298 hp, 2017. Rod ratio and piston speed.
The Ford 138ci is undersquare — the 3.7" stroke exceeds the 3.444" bore by 6.9% — a layout that trades peak RPM for leverage and torque low in the range. The 3.7" stroke puts mean piston speed at 4,000 ft/min around 6,500 RPM, which is where a production bottom end is generally considered at its limit. A rod ratio of 1.589 is in the range most production engines fall in. Each of the 4 cylinders displaces 34.5 ci (565 cc).
9.4:1 is low by modern standards and generally happy on regular pump fuel.
It is one of 5 engines in the Ford 138ci family, all of them 138 ci — the differences between them are in compression, heads and rating, not displacement.
| Displacement | 138 ci / 2.3 L |
|---|---|
| Bore | 3.444" |
| Stroke | 3.7" |
| Cylinders | 4 |
| Compression ratio | 9.4:1 |
| Rod length | 5.878" |
| Rod ratio | 1.589 |
| Bore/stroke ratio | 0.931 |
| Piston deck clearance | 0" |
| Advertised HP | 298 hp |
|---|---|
| Years | 2017 |
| Bore/stroke character | 0.931 — undersquare — stroke exceeds bore, which favours low-end torque |
|---|---|
| Mean piston speed at 6,000 RPM | 3,700 ft/min — in the range typical of performance street engines |
| Rod ratio | 1.589 — moderate — the range most production V8s fall in |
| Displacement per cylinder | 34.5 ci |
| Static compression | 9.4:1 — low by modern standards, generally happy on regular pump fuel |
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