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Mercury Q-code / R-code specs: 428 ci (7.0L) 8-cylinder, 4.13 x 3.984 in (104.9 x 101.2 mm) bore and stroke. Rated 335 hp, 1969–1970.
The Mercury Q-code / R-code is close to square: 4.1299" bore against 3.9843" stroke, within 3.7%, which splits the difference between a high-revving layout and a torque layout. The 3.9843" stroke puts mean piston speed at 4,000 ft/min around 6,000 RPM, which is where a production bottom end is generally considered at its limit. Each of the 8 cylinders displaces 53.5 ci (877 cc).
It is one of 34 engines in the FE family, the largest at 428 ci. 2 factory variants share these dimensions, rated at 335 hp across 1969–1970.
| Displacement | 428 ci / 7 L |
|---|---|
| Bore | 4.1299" |
| Stroke | 3.9843" |
| Cylinders | 8 |
| Configuration | V8 |
| Bore/stroke ratio | 1.037 |
| Block material | cast iron |
|---|---|
| Head material | cast iron |
| Valvetrain | OHV |
| Fuel type | gas |
| Advertised HP | 335 hp |
| Years | 1969–1970 |
| Bore/stroke character | 1.037 — square — bore and stroke are within 5%, a balanced compromise |
|---|---|
| Mean piston speed at 6,000 RPM | 3,984 ft/min — in the range typical of performance street engines |
| Displacement per cylinder | 53.5 ci |
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These records share identical bore, stroke, displacement and compression. They differ by model year and factory power rating.
| Year | Advertised HP | Code |
|---|---|---|
| 1969 | 335 hp | Q-code / R-code |
| 1970 | 335 hp | Q-code / R-code |