Chainsaw Repair

Here are some piston dimensions. 166 versus 111S from LeeH

Diameter 166 55.88 111S 55.89
Pin Diameter both 14mm
total height 166 49.50 111S 50.08
top of pin bore
to crown 166 17.50 111S 16.62 not counting crown
The 166 is a flat top, 111S is a domed piston
Put the pin through both pistons and the 166 is close to the top off
the 111S piston but the edge of the 166 is taller than the 111S so
it would make more compression providing there is room in the squish
band on the cylinder or have it machined.
I would say the 166 piston in a 111S would make more power.