The term "4 cylinder E" means an engine with four cylinders. Cylinders are the engine components where horsepower is generated when chemical energy from the combustion of gases is converted into mechanical energy that eventually moves the tractor.
Horsepower is the rate at which an engine produces the power that moves a vehicle. One horsepower equals 0.746 kilowatts (kw). The horsepower of the Ford 4000 four-cylinder E is 55 horsepower, which equals 41.0 kw. A few previous Ford tractor engines, such as the Ford 861, produced more horsepower, but most previous models produced less.
The drawbar is a metal bar to which machinery such as a drag or plow is attached at the back of the tractor. The drawbar horsepower is the horsepower that the engine actually transfers to the drawbar for the purpose of pulling a load. The drawbar horsepower of the Ford 4000 is 41 horsepower or 30.6 kw.