Mopar Main Bolt Kit 273-440

The ARP Mopar Main Bolt Kit 273-440 is a premium chromoly fastening solution engineered for small-block and big-block Mopar engine builds requiring maximum reliability under sustained cylinder pressure. Designed for two-bolt main applications across B-series and RB-series blocks, this kit addresses a critical weakness in stock cast-iron fasteners—bolt stretch and fatigue failure under high-RPM and forced-induction loads. Whether you're building a street performance 340, a competition 440, or a restomod engine, ARP main studs provide the clamping force consistency that separates a reliable powerplant from a catastrophic failure.

Each kit features ARP's proprietary chromoly steel construction with black oxide corrosion protection, offering superior tensile strength compared to OEM fasteners while maintaining precise torque-to-yield specifications essential for proper main cap sealing. The hex-nut design allows controlled tightening sequences that ensure uniform clamping load across the crankshaft, eliminating the micro-movement that weakens original equipment and causes bearing wear. ARP's quality control and shot-peening process significantly extend fatigue life, particularly critical in applications exceeding 6,000 RPM or featuring performance camshafts and high-lift valve trains that amplify main bearing stress.

Engine builders, restoration shops, and serious enthusiasts upgrading Mopar platforms benefit most from this kit when executing performance upgrades, addressing known casting defects in vintage blocks, or ensuring long-term durability in modified engines. Installation requires standard socket and torque wrench procedures; ARP supplies detailed torque specifications with each kit to guarantee proper preload. Compatible with all 273, 318, 340, 360, 361, 383, 400, and 440 Mopar engines utilizing the two-bolt main configuration, making this an industry-standard choice for both street and competition builds seeking OEM-equivalent reliability with measurably improved structural integrity.