This package includes the engine block assembly with main caps, main cap fasteners, and the block hardware kit. Some of the block hardware is installed in the block and some is included in a separate package with the block.

The R3 and R4 blocks are designed for use in racing where the engine builder does most of the final machine work (i.e. boring, honing, and camshaft bearing installation).

For builders who demand rugged durability, simple reliability, and a foundation that can handle serious power, the Mopar Performance Cast Iron Engine Blocks & Components in the small block lineup are the go-to choice. These cast iron blocks are built with race-proven strength, ready to take abuse in drag strip, circle track, or heavy-duty street applications.

Among the options is the legendary mopar r3 block—a cast iron race block designed with four-bolt mains on the center three caps, thick walls, and extra material in key areas for strength. Deck heights vary depending on your build goals, including shorter decks for dry-sump setups and tall decks for big-inch displacement, letting you tailor your build for RPM, torque, or compliance with class rules.

If you're actively shopping, you’ll see a number of mopar r3 block for sale that come in different combinations of tappet angles (48-degree or 59-degree), with either Siamese or full water jackets, and with machined features compatible with LA-style or Magnum motor mounts. These blocks often accept many stock components, which helps keep your build budget under control without compromising on toughness.

And of course, the storied 340 block is part of this ecosystem—offering a tried-and-true parts pool and interchangeability with many of your favorite Mopar small block components. Whether you want a cast block for high output or a replacement block for reliability and street use, these Mopar Performance cast iron small blocks deliver value, strength, and flexibility. Ready to start? The right block here sets the foundation for the rest of your engine build.