Stroke is defined as the distance the piston travels up and down inside the cylinder. If you switch to a stroker crank and rods, the piston moves further. That gets you more displacement. You don't really want to do this because it will make your car less eager to rev. The old B20A5 motor in the 3rd generation Prelude went this route to achieve its 2.0 liter displacement while using the same 81 mm bore as all of the other B-series motors and generally speaking people aren't such big fans of that motor. Its stroke is 95 mm as compared to 87.2 mm of the B18C for example. The B20B and B20Z which are the CR-V motors got their bigger displacement by running a wider 84 mm bore instead of the stock 81 mm bore. They have the same crank and rods as the LS motors (B18A1 and B18B1) but more displacement because of the wider bore.