Can I just swap crankshafts?
 

So I have a balanced and polished 91mm crankshaft sitting around.

Is it possible to just swap the 91mm shaft in for my stock 86mm?

I have a built SR with rods pistons bearings and ArP hardware. I want to swap in the 91mm shaft and make it a stroker motor.

Is it as simple as just installing the new shaft?

I've never dug into the bottom end before but it something I would like to learn as well.

If you add 5mm of stroke with a standard size rod and piston what do you think happens?

The answer is no, you'll need custom pistons designed for a 91mm stroke because they're shorter.