Mopar 6.1L Gen III Hemi Iron Block 9.250 x 4.090

The DART Mopar 6.1L Gen III Hemi Iron Block with 9.250 deck height and 4.090 bore is a bare iron block engineered for serious engine builders and performance shops targeting high-displacement stroker builds in Mopar platforms. This is foundational architecture—a bare casting supplied without pistons, rods, or internal components—that demands precision machine work and assembly expertise to realize its potential.

The 9.250-inch deck height accommodates modern piston and rod packages while the 4.090-inch bore diameter is sized for the Gen III Hemi platform architecture. The four-bolt main bearing cap design provides structural rigidity necessary for high-rpm operation and forced induction applications. The one-piece rear seal configuration simplifies crankshaft installation and reduces leak points common in two-piece designs. Cast iron construction offers thermal stability and bore wall durability under sustained high-boost or high-nitrous conditions—critical for engines intended to exceed stock output levels. Weighing 100 lbs as a bare casting, this block accepts standard Mopar crankshafts, rods, and accessory mounting provisions once machining is complete.

This block is specified for engine builders restoring or upgrading Dodge, Chrysler, and Jeep performance platforms that originally ran Gen III Hemi engines. Typical applications include street/strip vehicles requiring displacement increases, vintage muscle car restorations with modern powerplants, and purpose-built race engines where low-end cost and iron construction take priority over aluminum alternatives. Proper machining—deck surfacing, bore honing, and main cap alignment—is essential before assembly begins. Verification of bore condition and deck flatness is mandatory before ordering pistons and rods.

DART blocks occupy a recognized position in the OEM-based performance market, offering competitively priced casting alternatives to original Mopar inventory. The Gen III Hemi platform itself has proven durability across production vehicles and aftermarket race engines, making this block a practical foundation for builders familiar with the platform's machine work and assembly standards.