Crankshafts & Connecting Rods

Crankshafts and Connecting Rods for Performance Engine Builds

Your crankshaft and connecting rods work as a team, so you'll get the most from them when you choose them together. The crank converts the up-and-down motion of the pistons into rotation, and the rods link each piston to the crank. Combustion loads the rods in compression, while high RPM pulls on them in tension. If one part is weaker than the rest, it becomes the limit for the whole engine.

You'll find three main subcategories here:

• performance crankshafts in forged and cast steel for street and race engines
• performance connecting rods in H-beam and I-beam designs, including forged-steel options
• harmonic balancers that help control crankshaft vibration

Filters for material, brand, finish, and wrist pin style help you narrow the list fast. If you're still setting a budget, our guide to a budget vs. performance engine build can help you decide where your money matters most.

Forged vs. Cast-Steel Crankshafts

Choose a forged crankshaft for high RPM, boost, or nitrous, and a cast-steel crankshaft for a stock-style or mild street build. Forging aligns the steel's grain structure, which gives the crank more strength and fatigue resistance than casting. Casting costs less and suits many naturally aspirated street engines.

Eagle offers cast-steel crankshafts for 302 engines with a 3.000-inch stroke and for 351C engines, plus a steel crankshaft for LS engines. Scat builds a forged 4340 standard-weight crankshaft for 426 engines in a 6-bolt configuration. Crower offers a standard crankshaft for small-block engines.

Think about where your build is headed before you buy. If you plan to add a power adder later, a forged crank now can save you from replacing it twice. If the engine will stay mild, a cast-steel crank keeps more of your budget free for other parts.

H-Beam vs. I-Beam Connecting Rods

H-beam rods are generally the stronger pick for boost, nitrous, and high cylinder pressure, while I-beam rods suit high-RPM naturally aspirated builds. H-beam designs are stiffer and slightly heavier, so they resist bending when combustion loads spike. I-beam rods are lighter and handle tensile loads well, which helps when the engine spends time near redline. If you're running a power adder, start your search with H-beam rods.

Eagle SIR I-beam connecting rods are available for LS engines, and a forged 5140 steel version fits the 4.2L inline-six. Chevrolet Performance also offers an LS2/LS3 connecting rod. Use the Material and Wrist Pin Style filters to match rods to your pistons and power level.

Whichever beam style you pick, the fasteners deserve the same attention as the rod itself. Before you torque anything, read why rod bolts are critical in an engine build.

Harmonic Balancers and Crankshaft Accessories

A harmonic balancer dampens the crankshaft's torsional vibration, so you should match it to your engine whenever you change rotating parts or raise RPM. Each firing pulse twists the crank slightly. Left unchecked, that repeated twisting can fatigue the crank and the parts it drives. If you've added stroke or RPM, plan on a balancer that matches the new combination.

ATI Super Damper harmonic balancers cover small-block and big-block V8s, LS1 engines, 361-440 engines, and 1996-2004 4.6L applications. Use the Outside Diameter filter to narrow balancers to the size your accessory drive needs.

This category also carries crankshaft scrapers, hub spacers, and flexplate adapters. A crankshaft scraper helps strip oil away from the spinning crank. Hub spacers and flexplate adapters help you fit the balancer, accessory drive, and transmission to your combination. Check each part's listed fitment against your engine before you order.

How to Match Parts to Your Engine and Power Goals

Start with your target horsepower and RPM range, then pick a stroke, rod length, and material that support it. Stroke sets how far each piston travels, so a longer stroke adds displacement and torque. For example, Chevrolet Performance offers a forged crankshaft with a 4-inch stroke for the LS7.

Rod length has to work with the stroke, piston compression height, and block deck height. Get that wrong and the piston won't sit where it should at top dead center. You can skip that math with engine rotating assemblies, which pair the crank, rods, and pistons as a matched set.

If you're buying parts separately, add rod and main bearings and pistons and piston rings sized for your crank. For a broader plan, read about choosing the right short block for your horsepower goals, or shop all engines and engine components.