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Ford 1973 156 107HP specs: 156 ci (2.6L) 6-cylinder, 3.554 x 2.63 in (90.3 x 66.8 mm) bore and stroke, 9.8:1 compression. Rated 107 hp, 1973. OHV.
The Ford 1973 156 107HP is oversquare — the 3.554" bore exceeds the 2.63" stroke by 35.1% — a layout that favors airflow and RPM over leverage at the crank. The 2.63" stroke does not reach 4,000 ft/min of mean piston speed until about 9,150 RPM, so piston speed is not what limits this engine's revs — valvetrain and breathing are. A rod ratio of 1.954 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 26.0 ci (426 cc).
9.8:1 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 | 156 ci / 2.6 L |
|---|---|
| Bore | 3.554" |
| Stroke | 2.63" |
| Cylinders | 6 |
| Configuration | I6 |
| Compression ratio | 9.8:1 |
| Rod length | 5.14" |
| Rod ratio | 1.954 |
| Bore/stroke ratio | 1.351 |
| Piston deck clearance | 0.028" |
| Block material | cast iron |
|---|---|
| Head material | cast iron |
| Valvetrain | OHV |
| Fuel type | gas |
| Advertised HP | 107 hp |
| Years | 1973 |
| Bore/stroke character | 1.351 — oversquare — bore exceeds stroke, which favours higher RPM and larger valves |
|---|---|
| Mean piston speed at 6,000 RPM | 2,630 ft/min — conservative for a street engine |
| Rod ratio | 1.954 — long — less side loading on the cylinder wall, favours high RPM |
| Displacement per cylinder | 26.0 ci |
| Static compression | 9.8:1 — in the range that usually runs on pump premium |
| Intake valve diameter | 1.57" |
|---|---|
| Exhaust valve diameter | 1.27" |
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