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Chevrolet 235ci specs: 235 ci (3.9L) 6-cylinder, 3.563 x 3.938 in (90.5 x 100 mm) bore and stroke, 8.25:1 compression. Rated 135-145 hp, 1958–1959.
The Chevrolet 235ci 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).
8.25:1 is low by modern standards and generally happy on regular pump fuel.
It is one of 7 engines in the Chevrolet 235ci family, all of them 235 ci — the differences between them are in compression, heads and rating, not displacement. 2 factory variants share these dimensions, rated from 135 to 145 hp across 1958–1959.
| Displacement | 235 ci / 3.9 L |
|---|---|
| Bore | 3.563" |
| Stroke | 3.938" |
| Cylinders | 6 |
| Compression ratio | 8.25:1 |
| Rod length | 6.813" |
| Rod ratio | 1.73 |
| Bore/stroke ratio | 0.905 |
| Piston deck clearance | 0.014" |
| Induction | 1-1 |
|---|---|
| Advertised HP | 135–145 hp |
| Years | 1958–1959 |
| 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 | 8.25:1 — low by modern standards, generally happy on regular pump fuel |
| Intake valve diameter | 1.88" |
|---|---|
| Exhaust valve diameter | 1.505" |
| Chamber volume | 79.1 cc |
| Rocker ratio | 1.47:1 |
| Lifter type | hydraulic |
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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 |
|---|---|---|
| 1958 | 145 hp | — |
| 1959 | 135 hp | — |