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Ford 1976 171 100HP specs: 171 ci (2.8L) 6-cylinder, 3.661 x 2.70 in (93 x 68.6 mm) bore and stroke, 9.862:1 compression. Rated 100 hp, 1976.
The Ford 1976 171 100HP is oversquare — the 3.661" bore exceeds the 2.7" stroke by 35.6% — a layout that favors airflow and RPM over leverage at the crank. The 2.7" stroke does not reach 4,000 ft/min of mean piston speed until about 8,900 RPM, so piston speed is not what limits this engine's revs — valvetrain and breathing are. A rod ratio of 1.904 is long by production standards — less side-load on the cylinder wall and gentler piston acceleration around TDC, the geometry that tolerates high RPM. Each of the 6 cylinders displaces 28.5 ci (467 cc).
9.862:1 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.
It is one of 6 engines in the Ford 171ci family, all of them 171 ci — the differences between them are in compression, heads and rating, not displacement.
| Displacement | 171 ci / 2.8 L |
|---|---|
| Bore | 3.661" |
| Stroke | 2.7" |
| Cylinders | 6 |
| Configuration | I6 |
| Compression ratio | 9.862:1 |
| Rod length | 5.14" |
| Rod ratio | 1.904 |
| Bore/stroke ratio | 1.356 |
| Block material | cast iron |
|---|---|
| Head material | cast iron |
| Valvetrain | OHV |
| Fuel type | gas |
| Advertised HP | 100 hp |
| Years | 1976 |
| Bore/stroke character | 1.356 — oversquare — bore exceeds stroke, which favours higher RPM and larger valves |
|---|---|
| Mean piston speed at 6,000 RPM | 2,700 ft/min — conservative for a street engine |
| Rod ratio | 1.904 — long — less side loading on the cylinder wall, favours high RPM |
| Displacement per cylinder | 28.5 ci |
| Static compression | 9.862:1 — in the range that usually runs on pump premium |
| Intake valve diameter | 1.577" |
|---|---|
| Exhaust valve diameter | 1.276" |
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