"Unable to load engine, is too big."

[Imspartan9002]

This problem happens with any engine of any size, it's even happened with engines as tiny as under 1000cc, yet I still get this error.
It happens when I make a car body, then go on to make an engine, then finish the engine, only to realize it won't let me put it into the car.

[BlastersPewPew]

Thee are some cars where a transverse or longitudinal engine will NOT fit no matter what. Change to the other one and see if it fits.