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Plymouth K specs: 153 ci (2.5L) 4-cylinder, 3.661 x 3.622 in (93 x 92 mm) bore and stroke, 8.1:1 compression. Rated 224 hp. DOHC. Rod ratio and piston speed.
The Plymouth 2.2/2.5 (K) is close to square: 3.6614" bore against 3.622" stroke, within 1.1%, which splits the difference between a high-revving layout and a torque layout. The 3.622" stroke puts mean piston speed at 4,000 ft/min around 6,650 RPM, which is where a production bottom end is generally considered at its limit. Each of the 4 cylinders displaces 38.3 ci (627 cc).
8.1:1 on aluminum heads is low by modern standards and generally happy on regular pump fuel.
It is one of 8 engines in the 2.2/2.5 family, the largest at 153 ci. Factory fitments include the Plymouth Sundance Duster.
| Displacement | 153 ci / 2.5 L |
|---|---|
| Bore | 3.6614" |
| Stroke | 3.622" |
| Cylinders | 4 |
| Compression ratio | 8.1:1 |
| Bore/stroke ratio | 1.011 |
| Block material | cast iron |
|---|---|
| Head material | aluminum |
| Valvetrain | DOHC |
| Fuel type | gas |
| Advertised HP | 224 hp |
| Bore/stroke character | 1.011 — square — bore and stroke are within 5%, a balanced compromise |
|---|---|
| Mean piston speed at 6,000 RPM | 3,622 ft/min — in the range typical of performance street engines |
| Displacement per cylinder | 38.3 ci |
| Static compression | 8.1:1 — low by modern standards, generally happy on regular pump fuel |
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