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Chevrolet Blue-Flame 125 specs: 235 ci (3.9L) 6-cylinder, 3.563 x 3.938 in (90.5 x 100 mm) bore and stroke, 7.5:1 compression. Rated 125 hp, 1954.
The Chevrolet Blue-Flame 125 is undersquare — the 3.938" stroke exceeds the 3.563" bore by 9.5% — a layout that trades peak RPM for leverage and torque low in the range. The 3.938" stroke puts mean piston speed at 4,000 ft/min around 6,100 RPM, which is where a production bottom end is generally considered at its limit. A rod ratio of 1.73 is in the range most production engines fall in. Each of the 6 cylinders displaces 39.2 ci (642 cc).
7.5:1 is low by modern standards and generally happy on regular pump fuel.
It is one of 11 engines in the Chevrolet 235ci family, all of them 235 ci — the differences between them are in compression, heads and rating, not displacement.
| Displacement | 235 ci / 3.9 L |
|---|---|
| Bore | 3.563" |
| Stroke | 3.938" |
| Cylinders | 6 |
| Configuration | I6 |
| Compression ratio | 7.5:1 * |
| Rod length | 6.813" |
| Rod ratio | 1.73 |
| Bore/stroke ratio | 0.905 |
* Compression ratio from a single source; not yet cross-verified.
| Fuel type | gas |
|---|---|
| Advertised HP | 125 hp |
| Years | 1954 |
| Bore/stroke character | 0.905 — undersquare — stroke exceeds bore, which favours low-end torque |
|---|---|
| Mean piston speed at 6,000 RPM | 3,938 ft/min — in the range typical of performance street engines |
| Rod ratio | 1.73 — moderate — the range most production V8s fall in |
| Displacement per cylinder | 39.2 ci |
| Static compression | 7.5:1 — low by modern standards, generally happy on regular pump fuel |
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1 factory vehicle, 1954. Each year opens that model's engine table.