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Ford H-code / 351M specs: 351 ci (5.8L) 8-cylinder, 4.002 x 3.50 in (101.7 x 88.9 mm) bore and stroke. Built 1979. Used in the Ford F-150 and Ford Bronco.
The Ford H-code / 351M is oversquare — the 4.002" bore exceeds the 3.5" stroke by 14.3% — a layout that favors airflow and RPM over leverage at the crank. The 3.5" stroke puts mean piston speed at 4,000 ft/min around 6,850 RPM, which is where a production bottom end is generally considered at its limit. A rod ratio of 1.88 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 8 cylinders displaces 43.9 ci (719 cc).
It is one of 41 engines in the Ford 351ci family, all of them 351 ci — the differences between them are in compression, heads and rating, not displacement.
| Displacement | 351 ci / 5.8 L |
|---|---|
| Bore | 4.002" |
| Stroke | 3.5" |
| Cylinders | 8 |
| Configuration | V8 |
| Compression ratio | 8–8.3:1 (published figures vary) |
| Rod length | 6.58" |
| Rod ratio | 1.88 |
| Bore/stroke ratio | 1.143 |
| Deck height | 10.297" |
| Block material | cast iron |
|---|---|
| Head material | cast iron |
| Valvetrain | OHV |
| Fuel type | gas |
| Firing order | 1-3-7-2-6-5-4-8 |
| Years | 1979 |
| Bore/stroke character | 1.143 — oversquare — bore exceeds stroke, which favours higher RPM and larger valves |
|---|---|
| Mean piston speed at 6,000 RPM | 3,500 ft/min — conservative for a street engine |
| Rod ratio | 1.88 — long — less side loading on the cylinder wall, favours high RPM |
| Displacement per cylinder | 43.9 ci |
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3 factory vehicles, 1977–1982. Each year opens that model's engine table.