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Ford 1997 155 170HP specs: 155 ci (2.5L) 6-cylinder, 3.24 x 3.13 in (82.3 x 79.5 mm) bore and stroke, 10.5:1 compression. Rated 170 hp, 1997. OHV.
The Ford 1997 155 170HP is close to square: 3.24" bore against 3.13" stroke, within 3.5%, which splits the difference between a high-revving layout and a torque layout. The 3.13" stroke does not reach 4,000 ft/min of mean piston speed until about 7,650 RPM, so piston speed is not what limits this engine's revs — valvetrain and breathing are. A rod ratio of 1.737 is in the range most production engines fall in. Each of the 6 cylinders displaces 25.8 ci (423 cc).
10.5:1 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.
| Displacement | 155 ci / 2.5 L |
|---|---|
| Bore | 3.24" |
| Stroke | 3.13" |
| Cylinders | 6 |
| Configuration | I6 |
| Compression ratio | 10.5:1 |
| Rod length | 5.437" |
| Rod ratio | 1.737 |
| Bore/stroke ratio | 1.035 |
| Piston deck clearance | 0.004" |
| Block material | cast iron |
|---|---|
| Head material | cast iron |
| Valvetrain | OHV |
| Fuel type | gas |
| Advertised HP | 170 hp |
| Years | 1997 |
| Bore/stroke character | 1.035 — square — bore and stroke are within 5%, a balanced compromise |
|---|---|
| Mean piston speed at 6,000 RPM | 3,130 ft/min — conservative for a street engine |
| Rod ratio | 1.737 — moderate — the range most production V8s fall in |
| Displacement per cylinder | 25.8 ci |
| Static compression | 10.5:1 — in the range that usually runs on pump premium |
| Intake valve diameter | 1.26" |
|---|---|
| Exhaust valve diameter | 1.024" |
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