ARP 12-Point Harmonic Balancer Bolt Kit for Small Block Chevy

The ARP Harmonic Balancer Bolt Kit provides a high-strength replacement fastener for securing the harmonic balancer, also called the harmonic damper, to a traditional Chevrolet small-block crankshaft.

The kit features a 7/16-20 bolt manufactured from heat-treated 8740 chromoly with a black oxide finish. Its extra-tall 12-point head provides convenient tool engagement, while the included wide-area hardened washer distributes clamping load across the face of the harmonic balancer.

Features

• Harmonic balancer and damper retaining bolt kit
• Designed for traditional Chevrolet small-block engines
• Manufactured from high-strength 8740 chromoly
• Black oxide finish
• Extra-tall 12-point head
• Includes a wide-area hardened washer
• 7/16-20 thread size
• 2.470-inch underhead length
• ARP part number 234-2501

Fitment

Designed for traditional Chevrolet small-block engines using a 7/16-20 threaded crankshaft snout. Common applications may include compatible 265, 283, 302, 305, 307, 327, 350, 383, and 400 cubic-inch small-block combinations.

Engine displacement alone does not guarantee compatibility. Confirm the crankshaft thread size, required bolt length, washer clearance, and harmonic balancer configuration before ordering—especially when using an aftermarket crankshaft or balancer.

This kit is not intended for Chevrolet Gen III or Gen IV LS-series engines, which use a different harmonic balancer bolt. It should also not be selected for a Gen V LT engine based solely on the Chevrolet small-block designation.

Specifications

• Application: Harmonic balancer or harmonic damper
• Thread size: 7/16-20
• Underhead length: 2.470 inches
• Head style: 12-point
• Required socket: 13/16-inch 12-point
• Bolt material: 8740 chromoly
• Finish: Black oxide
• Washer included: Yes

Recommended Use

Recommended when installing or replacing a harmonic balancer on a compatible Chevrolet small-block engine. The high-strength bolt and large hardened washer are suitable for stock restoration, street-performance, racing, naturally aspirated, and forced-induction engine builds when the listed dimensions match the application.

What’s Included

• 1 ARP 12-point harmonic balancer bolt
• 1 hardened wide-area washer
• ARP part number 234-2501

The harmonic balancer, installation tool, crankshaft, and other engine components are not included.

Installation

Before installation, confirm the bolt’s dimensions and inspect it for damage. Clean the internal threads at the end of the crankshaft to remove debris, corrosion, old threadlocker, and contamination. Chase the threads when necessary, taking care not to damage or remove material from the crankshaft.

Apply ARP Ultra-Torque Fastener Assembly Lubricant to the bolt threads, beneath the bolt head, and to the front surface of the balancer where the washer makes contact. Install the washer and start the bolt by hand to prevent cross-threading.

ARP specifies tightening the balancer bolt to 80 ft-lb when ARP Ultra-Torque is used. A different lubricant or dry installation can change the resulting clamp load and should not be substituted without obtaining the appropriate torque specification.

Use the proper harmonic balancer installation tool when pressing the balancer onto the crankshaft. Do not use the retaining bolt as a substitute for a balancer installation tool unless the engine or balancer manufacturer specifically authorizes that procedure.