In the days of old, when the venerable Rover/Buick derived V8 engine was in it's infancy during the gestation period, the engine is attached to the maternal placenta using an umbilical cord.
The carrier and the infant share the same oil system, fuel source and induction air input, all of which are transferred using the process of osmosis through this connected tube.
Whilst it is considered by some necessary to cut this tube following the completion of the infants gestation very close to the new born, this causes an 'Inney' whilst a cut made further from the infant can be represented as an 'Outy'.
The length of tube is deemed very important especially to the male version of the Engine, often times referred to by the name Thor, whilst it is more the girth of the tube that is more important to the female version of the Engine, often referred to as Gems.
Thor and Gems start out as the same engine, atleast from the bottom half, but as you move through to the top half of the engine, the subtle differences between the sexes becomes more apparent, most notable the Thor (male) engine as a very prominent muscular looking plenum chamber and induction manifold, whilst the female Gems, as a more sleek refined plenum.