Displacement Is Geometry
Formula
Displacement = π/4 × bore² × stroke × cylinders.
That is why a 4.8 and 5.3 can share a 3.780-inch bore but differ in displacement: the 4.8 uses about a 3.267-inch stroke while the 5.3 uses about 3.622 inches.
Common LS Geometry
| Example | Bore | Stroke | Approx. CID | Notes |
|---|---|---|---|---|
| 4.8 | 3.780 | 3.267 | 293 | Short-stroke truck combination |
| 5.3 | 3.780 | 3.622 | 325 | Common truck combination |
| 6.0 | 4.000 | 3.622 | 364 | 4.000-inch bore opens many head choices |
| 6.2 | 4.065 | 3.622 | 376 | Factory LS3/L92-family geometry |
| LS7 | 4.125 | 4.000 | 427 | Factory 7.0L geometry |
| 4.000 bore × 4.000 stroke | 4.000 | 4.000 | 402 | Common aftermarket “402” geometry |
| 4.065 bore × 4.000 stroke | 4.065 | 4.000 | 415 | Common aftermarket 6.2-based stroker geometry |
| 4.070 bore × 4.000 stroke | 4.070 | 4.000 | 416 | Often called a 416; final size depends on actual finish bore |
Static Compression Ratio
CR = (swept volume + clearance volume) ÷ clearance volume. Clearance volume includes chamber volume, piston dish/dome, head-gasket volume and deck-clearance volume. Milling a head, thinner gasket, smaller chamber or reduced piston dish generally raises static compression.
Do not pick compression from a forum number alone. Fuel octane, combustion chamber, cam intake closing, charge temperature, boost, quench, vehicle load and calibration all affect knock margin. Static compression is only one piece.
Stroker Planning Checklist
- Confirm the block can safely support the intended finish bore; sonic-check when the combination warrants it.
- Check crank counterweight/block/piston clearance.
- Match rod length, compression height and deck target.
- Calculate actual compression from measured component volumes.
- Verify piston-to-valve clearance with the selected cam and installed position.
- Balance the rotating assembly as a complete combination.