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Cadillac 429 specs: 429 ci (7.0L) 8-cylinder, 4.25 x 3.752 in (108 x 95.3 mm) bore and stroke, 10.5:1 compression. Rated 340 hp. Rod ratio and piston speed.
The Cadillac OHV V8 (429) is oversquare — the 4.25" bore exceeds the 3.752" stroke by 13.3% — a layout that favors airflow and RPM over leverage at the crank. The 3.752" stroke puts mean piston speed at 4,000 ft/min around 6,400 RPM, which is where a production bottom end is generally considered at its limit. Each of the 8 cylinders displaces 53.6 ci (879 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.
It is one of 4 engines in the Cadillac OHV V8 family, sitting between the 390 ci and 500 ci members. Factory fitments include the Cadillac DeVille, Cadillac Fleetwood, Cadillac Calais and 3 others.
| Displacement | 429 ci / 7 L |
|---|---|
| Bore | 4.25" |
| Stroke | 3.752" |
| Cylinders | 8 |
| Compression ratio | 10.5:1 |
| Bore/stroke ratio | 1.133 |
| Block material | cast iron |
|---|---|
| Head material | cast iron |
| Valvetrain | OHV |
| Fuel type | gas |
| Advertised HP | 340 hp |
| Bore/stroke character | 1.133 — oversquare — bore exceeds stroke, which favours higher RPM and larger valves |
|---|---|
| Mean piston speed at 6,000 RPM | 3,752 ft/min — in the range typical of performance street engines |
| Displacement per cylinder | 53.6 ci |
| Static compression | 10.5:1 — in the range that usually runs on pump premium |
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