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GMC 235 specs: 235 ci (3.85L) 6-cylinder, 3.875 x 3.313 in (98.4 x 84.1 mm) bore and stroke, 7.5:1 compression. Rated 105 hp. OHV. Rod ratio and piston speed.
The GMC Chevy Straight-6 (235/261) (235) is oversquare — the 3.8752" bore exceeds the 3.3126" stroke by 17.0% — a layout that favors airflow and RPM over leverage at the crank. The 3.3126" stroke does not reach 4,000 ft/min of mean piston speed until about 7,250 RPM, so piston speed is not what limits this engine's revs — valvetrain and breathing are. Each of the 6 cylinders displaces 39.2 ci (642 cc).
7.5:1 on iron heads is low by modern standards and generally happy on regular pump fuel.
It is one of 3 engines in the Chevy Straight-6 (235/261) family, the smallest at 235 ci. Factory fitments include the Chevrolet Advance Design trucks, Chevrolet Task Force trucks, Chevrolet Bel Air and 2 others.
| Displacement | 235 ci / 3.85 L |
|---|---|
| Bore | 3.8752" |
| Stroke | 3.3126" |
| Cylinders | 6 |
| Compression ratio | 7.5:1 |
| Bore/stroke ratio | 1.17 |
| Block material | cast iron |
|---|---|
| Head material | cast iron |
| Valvetrain | OHV |
| Fuel type | gas |
| Advertised HP | 105 hp |
| Bore/stroke character | 1.170 — oversquare — bore exceeds stroke, which favours higher RPM and larger valves |
|---|---|
| Mean piston speed at 6,000 RPM | 3,313 ft/min — conservative for a street engine |
| 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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