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Chevrolet Trademaster 265 specs: 265 ci (4.3L) 8-cylinder, 3.75 x 3.00 in (95.3 x 76.2 mm) bore and stroke. Rated 145-155 hp, 1955–1957.
The Chevrolet Trademaster 265 is oversquare — the 3.75" bore exceeds the 3" stroke by 25.0% — a layout that favors airflow and RPM over leverage at the crank. The 3" stroke does not reach 4,000 ft/min of mean piston speed until about 8,000 RPM, so piston speed is not what limits this engine's revs — valvetrain and breathing are. A rod ratio of 1.988 is long by production standards — less side-load on the cylinder wall and gentler piston acceleration around TDC, the geometry that tolerates high RPM. Each of the 8 cylinders displaces 33.1 ci (543 cc).
It is one of 2 engines in the Chevrolet 265ci family, all of them 265 ci — the differences between them are in compression, heads and rating, not displacement. 3 factory variants share these dimensions, rated from 145 to 155 hp across 1955–1957.
| Displacement | 265 ci / 4.3 L |
|---|---|
| Bore | 3.75" |
| Stroke | 3" |
| Cylinders | 8 |
| Configuration | V8 |
| Rod length | 5.964" |
| Rod ratio | 1.988 |
| Bore/stroke ratio | 1.25 |
| Block material | cast iron |
|---|---|
| Head material | cast iron |
| Valvetrain | OHV |
| Fuel type | gas |
| Advertised HP | 145–155 hp |
| Years | 1955–1957 |
| Bore/stroke character | 1.250 — oversquare — bore exceeds stroke, which favours higher RPM and larger valves |
|---|---|
| Mean piston speed at 6,000 RPM | 3,000 ft/min — conservative for a street engine |
| Rod ratio | 1.988 — long — less side loading on the cylinder wall, favours high RPM |
| Displacement per cylinder | 33.1 ci |
Each link opens the calculator with this engine's specs already filled in.
These records share identical bore, stroke, displacement and compression. They differ by model year and factory power rating.
| Year | Advertised HP | Code |
|---|---|---|
| 1955 | 145 hp | Trademaster 265 |
| 1956 | 155 hp | Trademaster 265 |
| 1957 | 155 hp | Trademaster 265 |