Garage 54 wanted to find out how much faster a Lada Riva could accelerate with another engine. They started by sourcing a second inline-four from a Lada 2101. They welded the front pulley from the rear engine to the pressure plate of the front engine. Then they built a simple cradle out of square tubing that holds the front engine. The combined engine make a total displacement of 2.7 liters. If you want to jump ahead and see how crazy this project becomes, you can watch newer videos on their main channel.
Source: Garage 54 ENG via BangShift