Editing Four-stroke engine (section)

=== Rod and piston-to-stroke ratio ===
The rod-to-stroke ratio is the ratio of the length of the [[connecting rod]] to the length of the piston stroke. A longer rod reduces sidewise pressure of the piston on the cylinder wall and the stress forces, increasing engine life. It also increases the cost and engine height and weight.

A "square engine" is an engine with a bore diameter equal to its stroke length. An engine where the bore diameter is larger than its stroke length is an [[oversquare]] engine, conversely, an engine with a bore diameter that is smaller than its stroke length is an undersquare engine.