Vortec is a trademarked name for a line of gasoline engines for General Motors trucks.
The name first appeared in an advertisement for the 1985 model year 4.3 L V6 that used "vortex technology" to create a vortex inside the combustion chamber, creating a better air / fuel atomization.
[1] It has since been used on a wide range of engines.
Modern Vortec engines are named for their approximate displacement in cubic centimeters.