Bearing caps literally keep the bottom from falling out of your engine.  At Eliminator Performance Products, we take our caps seriously to keep your crankshaft in place and running true.  We have both Cast and Billet caps available. In this image, you can see the difference between a Cast (top) and a Billet (bottom) bearing cap.  The Cast cap is molded from molten steel and is then machined on critical bearing surfaces, while the Billet cap is entirely machined from a solid block (billet) of steel.  Generally, the Billet cap surface finish is much more precise, and it can be tempered to have greater strength.