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Oldsmobile 455ci (1968–1976) specs: 455 ci (7.5L) 8-cylinder, 4.126 x 4.25 in (104.8 x 108 mm) bore and stroke. Rated 310-375 hp, 1968–1976.
The Oldsmobile 455ci (1968–1976) is close to square: 4.126" bore against 4.25" stroke, within 2.9%, which splits the difference between a high-revving layout and a torque layout. The 4.25" stroke puts mean piston speed at 4,000 ft/min around 5,650 RPM, which is where a production bottom end is generally considered at its limit. A rod ratio of 1.585 is in the range most production engines fall in. Each of the 8 cylinders displaces 56.9 ci (932 cc).
It is one of 15 engines in the Oldsmobile 455ci family, all of them 455 ci — the differences between them are in compression, heads and rating, not displacement. 17 factory variants share these dimensions, rated from 310 to 375 hp across 1968–1976.
| Displacement | 455 ci / 7.5 L |
|---|---|
| Bore | 4.126" |
| Stroke | 4.25" |
| Cylinders | 8 |
| Configuration | V8 |
| Compression ratio | 8.5–10.25:1 (published figures vary) |
| Rod length | 6.735" |
| Rod ratio | 1.585 |
| Bore/stroke ratio | 0.971 |
| Block material | cast iron |
|---|---|
| Head material | cast iron |
| Valvetrain | OHV |
| Fuel type | gas |
| Firing order | 1-8-4-3-6-5-7-2 |
| Advertised HP | 310–375 hp |
| Years | 1968–1976 |
| Year | Version | HP @ rpm | Torque @ rpm | Comp. | Duration int / exh | Valve lift int / exh | LSA |
|---|---|---|---|---|---|---|---|
| 1968 | L30 gross | 310 @ 4200 | 490 lb-ft @ 2400 | 9:1 | — | — | — |
| 1968 | L66 gross | 320 @ 4200 | 500 lb-ft @ 2400 | 10.25:1 | — | — | — |
| 1968 | L31 gross | 365 @ 4600 | 510 lb-ft @ 3000 | 10.25:1 | — | — | — |
| 1968 | gross | 375 @ 4600 | 510 lb-ft @ 3000 | 10.25:1 | — | — | — |
| 1969 | gross | 310 @ 4200 | 490 lb-ft @ 2400 | 9:1 | — | — | — |
| 1969 | L31 gross | 365 @ 4600 | 510 lb-ft @ 3000 | 10.25:1 | — | — | — |
| 1969 | gross | 375 @ 4600 | 510 lb-ft @ 3000 | 10.25:1 | — | — | — |
| 1970 | L30 gross | 310 @ 4200 | 490 lb-ft @ 2400 | 9:1 | — | — | — |
| 1970 | L31 gross | 365 @ 4600 | 510 lb-ft @ 3000 | 10.25:1 | — | — | — |
| 1970 | gross | 375 @ 4600 | 510 lb-ft @ 3000 | 10.25:1 | — | — | — |
| 1971 | L31 gross | 320 @ 4400 | 460 lb-ft @ 2800 | 8.5:1 | — | — | — |
| 1971 | gross | 340 @ 4600 | 460 lb-ft @ 3200 | 8.5:1 | 294° / 296° | 0.472" | 113.5° |
| 1971 | W30 gross | 350 @ 4700 | 460 lb-ft @ 3200 | 8.5:1 | 328° | 0.475" | 110° |
Factory specification sheet. Durations are the factory's advertised figures at the basis printed on the sheet, not duration at .050" lift; lobe separation is calculated from the printed valve timing.
| Bore/stroke character | 0.971 — square — bore and stroke are within 5%, a balanced compromise |
|---|---|
| Mean piston speed at 6,000 RPM | 4,250 ft/min — in the range typical of performance street engines |
| Rod ratio | 1.585 — moderate — the range most production V8s fall in |
| Displacement per cylinder | 56.9 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 |
|---|---|---|
| 1968 | 310 hp | — |
| 1968 | 320 hp | — |
| 1968 | 365 hp | — |
| 1968 | 375 hp | — |
| 1969 | 310 hp | — |
| 1969 | 365 hp | — |
| 1969 | 375 hp | — |
| 1970 | 310 hp | — |
| 1970 | 365 hp | — |
| 1970 | 375 hp | — |
| 1971 | 320 hp | — |
| 1971 | 340 hp | — |
| 1971 | 350 hp | — |
| 1973 | — | — |
| 1974 | — | — |
| 1975 | — | — |
| 1976 | — | — |
4 factory vehicles, 1968–1976. Each year opens that model's engine table.