An engine's stroke is the distance the piston travels inside the cylinder. Stroke length is determined by the crankshaft. It can be listed in either inches or millimeters.
How is it measured?
The best way to find the stroke length is to:
- Identify the crankshaft.
- Brand, model, part number, and/or other information will be stamped or etched on the crank.
- Look up the specifications online.
- OR - - Contact the manufacturer.
Another option is to have the crankshaft checked by the machine shop.
Finally, stroke length can be measured with a set of Dial Calipers and a Deck Bridge. This method will give you an idea of the stroke. But it is not as accurate as the other methods.
- Install dial caliper (jaws upward) on the deck bridge.
- With piston at TDC, place bridge over cylinder.
- Zero dial calipers on the piston deck.
- Rotate the crankshaft until the piston is at BDC.
- Open dial calipers until depth rod is contacting piston deck clearance.
**The measurement on the dial calipers is the stroke.**
How does it affect performance?
Stroke length will impact an engine's fuel efficiency and power output. Stroke length is also an important measurement used to calculate Engine Displacement.
| Longer Stroke | Shorter Stroke |
| Increases displacement | Decreases displacement |
| Increases torque and power | Peak power at higher rpm |
| Uses more fuel | Uses less fuel |
| Slower to rev up to max rpm | Faster to rev up to max rpm |
| Operates in a lower rpm range |