The block is machined from a piece of forged aluminum. It has press-fitted, ductile iron liners. There are no water passages in the block, which adds considerable strength and stiffness. The engine is cooled by the incoming air/fuel mixture and the lubricating oil. Like the original Hemi, the racing cylinder block has a deep skirt for strength. There are five main bearing caps, which are fastened with aircraft-standard-rated steel studs, with additional reinforcing main studs and side bolts ("cross-bolting"). There are three approved suppliers of these custom blocks.