Hi, first plane, first engine, first post here.
I am a raw newbie, but bought a plane from a m8 which has an Irvine 40 engine.
Despite knowing nothing, I stripped down the engine,(great idea for a newbie ) and cleaned it up with carburettor spray.
I think I know how to put it back , but am not 100% sure about "which way around" the piston goes.

The piston has a little rectangle cut out in it , so could anyone describe which way around in the sleeve it goes.

Also as the engine is bone dry now, do I need to oil it before trying to start it etc, will I need a torque spanner to put the head back on etc.
Any advice appreciated, cos I know nothing ( didn't stop me taking it apart though).