Engine Connecting Rod

What Are Engine Connecting Rods and Why Do They Matter?

The connecting rod is one of the most mechanically stressed components inside any internal combustion engine. Tasked with linking the reciprocating piston to the rotating crankshaft, each rod must endure tremendous tensile and compressive forces on every single firing event — multiplied tens of millions of times over the life of the engine. Whether you're rebuilding a stock motor or assembling a high-horsepower forced-induction monster, the quality of your connecting rod assembly — the rods themselves, their bearings, and their fasteners — directly determines how reliable and capable your engine will be.

The connecting rod "assembly" is really a system of three interdependent components: the rod body, the rod bearings (which cushion the interface between the rod journal and the crankshaft), and the rod bolts (which clamp the rod cap and must resist the violent reciprocating forces at every TDC and BDC event). Upgrading any one of these without considering the others is a recipe for failure. That's why serious engine builders source all three from proven, performance-focused manufacturers.

Key Considerations When Shopping Connecting Rods

• Material and beam design: I-beam rods excel under tension (high-RPM, naturally aspirated builds), while H-beam designs offer greater compressive strength for high-boost, high-torque applications.
• Rod bolt grade: The rod bolt is the critical fastener holding the cap in place. Bolt stretch — not just torque — must be monitored during assembly and checked at every rebuild.
• Bearing metallurgy: Tri-metal and bimetal bearings each have different fatigue and load-carrying characteristics. Match the bearing type to your power level and duty cycle.
• Application fit: Always verify bore diameter, center-to-center length, and pin diameter for your specific engine before ordering.

Top Brands in Engine Connecting Rods

ARP is the industry gold standard for connecting rod fasteners. ARP rod bolts are made from seamless, defect-free 8740 chromoly steel, heat-treated before grinding and thread rolling, and are used in applications ranging from stock replacement all the way to NASCAR, IHRA, and NHRA competition. In fact, many connecting rod manufacturers spec ARP hardware as standard equipment straight from the factory — a testament to their reputation. At extreme power levels, ARP's exotic alloy lines — including ARP2000 and Custom Age 625+ — deliver tensile strengths up to 260,000–280,000 psi for Formula 1 and endurance racing applications.

ACL Bearings brings more than a half-century of race bearing engineering to the connecting rod category. Their Race Series rod bearings feature hardened steel backs, high-strength overlay plates with reduced thickness for improved fatigue properties, and increased eccentricity to compensate for bore distortion at high RPM. ACL's Race Series bearings have been standard components in engines that have set records and won championships across drag racing, road racing, and oval competition worldwide.

Manley Performance has been building performance engine internals since 1966 and offers one of the most comprehensive connecting rod lineups in the industry — from their Sportsmaster street rods all the way to the Pro Series Turbo Tuff I-beam rods engineered for turbocharged, supercharged, and nitrous-fed applications. Manley connecting rods are manufactured from high-quality 4340 or 300M steel depending on the application, and are shot-peened and magnafluxed for quality assurance. Many Manley rod sets are also equipped with ARP hardware as standard, combining two of the industry's most trusted names in a single assembly.