Build in a Box.

As a fuel-injected, hydraulic roller-cam unit, these cores have an exceptional life span, including a low incidence of ring/ bore and cam lobe wear due to the superior fuel control from EFI and the low friction of the roller cam. No engine family in history has played a bigger role in hot rodding life than the small-block Chevy. Vortec Heads and Hydraulic Roller Cam = Cheap HP Of critical importance here is that a Vortec crate engine may be rebuilt with a flat-tappet cam - that's going backwards just to save dollars. [Extracted from the article]