GMC 421 Specs
GMC 421 engine specs: 421 ci (6.9L), 8-cylinder, 4.1882" bore x 3.7" stroke, 10.75:1 compression.
Dimensions
| Displacement | 421 ci / 6.9 L |
|---|
| Bore | 4.1882" |
|---|
| Stroke | 3.7" |
|---|
| Cylinders | 8 |
|---|
| Compression ratio | 10.75:1 |
|---|
| Bore/stroke ratio | 1.132 |
|---|
Construction
| Block material | cast iron |
|---|
| Head material | cast iron |
|---|
| Valvetrain | OHV |
|---|
| Fuel type | gas |
|---|
| Advertised HP | 370 hp |
|---|
What these numbers mean
| Bore/stroke character | 1.132 — oversquare — bore exceeds stroke, which favours higher RPM and larger valves |
|---|
| Mean piston speed at 6,000 RPM | 3,700 ft/min — in the range typical of performance street engines |
|---|
| Displacement per cylinder | 52.6 ci |
|---|
| Static compression | 10.75:1 — in the range that usually runs on pump premium |
|---|
Run the numbers for this engine
Each link opens the calculator with this engine's specs already filled in.
Vehicles (3)
- Pontiac Catalina
- Pontiac Grand Prix
- Pontiac GTO
Similar engines
← All Pontiac V8 engines