ARP 640-0515 Black Oxide 1/4-20″ RH Thread 0.515″ UHL 12-Point Bolt with 5/16″ Socket and Washer, (Set of 5)

Description

Product Overview

The ARP 640-0515 black oxide bolt set is engineered for the most demanding automotive applications where precision, strength, and reliability are non‑negotiable. Each of the five bolts measures 1/4-20 RH thread and features a 12-point hex head that accepts a 5/16-inch socket, allowing quick installation and removal without sacrificing torque. The bolts are finished in a durable black oxide coating that resists corrosion and blends seamlessly with typical engine bay aesthetics. Constructed from Grade 8 stainless steel, the fasteners deliver a minimum shear strength of 55 MPa, ensuring they can withstand the high‑load environments found in performance engines, transmission mounts, and critical chassis connections. The included washers distribute load evenly across mating surfaces, reducing the risk of deformation and extending the service life of both the bolt and the components it secures. Designed to meet ARP’s exacting standards, this set provides the confidence of factory‑grade quality while offering the convenience of a ready‑to‑install package.
From a metallurgical perspective, the ARP 640‑0515 bolts are forged from a high‑grade stainless alloy that combines chromium, molybdenum, and nickel to achieve a balance of tensile strength and ductility. The forging process aligns the grain structure along the bolt axis, which enhances resistance to fatigue cracking under cyclic loading. After forging, the bolts undergo a controlled heat‑treatment cycle that raises the hardness to the Grade 8 specification while preserving the material’s toughness. The final black oxide conversion coating is applied in a low‑temperature bath, ensuring that the underlying microstructure is not altered, thereby maintaining the bolt’s mechanical properties. This comprehensive manufacturing approach results in a fastener that not only meets but exceeds the performance expectations of professional racers and engine builders.
The design of the ARP 640‑0515 set also takes into account the ergonomics of the installation process. The 12‑point hex head provides a larger contact surface for the socket, reducing the amount of force required to achieve the same torque compared with traditional 6‑point heads. This feature minimizes the risk of hand fatigue during prolonged assembly tasks and allows for more precise torque control, which is essential when working with high‑performance engines that demand exact fastener preload. Additionally, the black oxide coating reduces glare in the engine bay, making it easier for technicians to locate and align the bolts during complex builds.

Usage

These bolts are ideally suited for a wide range of performance‑oriented tasks, from installing aftermarket camshafts and oil pumps to reinforcing engine block brackets and transmission mounts. The 1/4‑20 thread size is a common specification in many American‑made engines, making the set a versatile addition to any mechanic’s toolbox. Whether you are rebuilding a classic muscle car, upgrading a modern sports sedan, or performing routine maintenance on a high‑output race engine, the ARP 640‑0515 bolts provide the secure clamping force required to keep critical components locked in place under extreme vibration and thermal cycling. The integrated socket design eliminates the need for separate wrenches, speeding up assembly time and reducing the chance of rounding off the bolt head. Because the bolts are made from stainless steel, they maintain their structural integrity even after repeated exposure to oil, coolant, and high temperatures, making them a reliable choice for both street and track use.
In turbocharged applications, the 640‑0515 bolts are frequently used to secure intercooler brackets, wastegate actuators, and oil feed lines where precise alignment and leak‑free connections are critical. Their 12‑point hex heads allow technicians to apply the recommended torque using standard socket wrenches, while the integrated washers help to seal the joint against oil seepage. For high‑revving V8 or V12 engines, the bolts can be employed in camshaft bearing caps and timing cover fasteners, where the combination of high shear strength and corrosion resistance ensures that the timing components remain locked throughout the engine’s operating range. The versatility of the 1/4‑20 thread also makes the set suitable for custom fabrications, such as mounting lightweight aluminum subframes or reinforcing chassis components in off‑road vehicles.
Regular maintenance of the bolt set is straightforward. Because the bolts are made from stainless steel, they do not require frequent re‑application of anti‑seize compounds, though a thin layer of high‑temperature lubricant can be used to achieve the specified torque values. When inspecting the bolts during routine service intervals, look for signs of wear on the socket interface or any discoloration of the black oxide finish, which may indicate exposure to excessive heat. In most cases, the bolts will retain their structural integrity for the lifetime of the vehicle, provided they are not subjected to overtightening beyond the manufacturer’s recommended torque specifications.

Why Choose Us

Choosing the ARP 640‑0515 set means selecting a product that embodies decades of engineering expertise and a commitment to quality that is unmatched in the aftermarket fastener market. ARP’s reputation for producing high‑strength, aerospace‑grade hardware translates directly into the durability and performance of these bolts, which are tested to exceed standard automotive specifications. The black oxide finish not only provides a sleek, professional appearance but also adds an extra layer of protection against rust and wear, extending the lifespan of the fastener in harsh environments. Each bolt is individually inspected and heat‑treated to guarantee consistent hardness and tensile strength, ensuring that you receive a product that performs exactly as advertised.
ARP’s commitment to continuous improvement means that each production batch incorporates the latest advances in metallurgy and surface treatment technology. The black oxide coating applied to the 640‑0515 bolts is a result of a controlled chemical conversion process that creates a uniform, non‑conductive layer resistant to moisture and chemical exposure. This treatment not only enhances the aesthetic appeal but also reduces the likelihood of galvanic corrosion when the bolts are used in conjunction with aluminum or alloy components. Moreover, the company’s extensive testing protocols include torque‑to‑yield analysis, fatigue testing, and environmental exposure simulations, all of which verify that the bolts will perform reliably under the most demanding conditions.
ARP’s customer support team is staffed by engineers who specialize in fastener technology and can provide detailed installation guidelines, torque charts, and troubleshooting advice for any application. The company’s lifetime warranty covers defects in material and workmanship, giving users confidence that the bolts will perform as intended for the life of the vehicle. In the rare event that a bolt fails under normal operating conditions, ARP will replace the part at no cost, reinforcing the brand’s commitment to durability and customer satisfaction. This level of service is especially valuable for professional shops that rely on dependable components to maintain their reputation for quality workmanship.

Key Features

• Five 1/4-20 RH thread bolts with integrated 5/16-inch socket heads for fast, tool-free installation.
• Grade 8 stainless steel construction provides a minimum shear strength of 55 MPa and excellent corrosion resistance.
• Durable black oxide finish protects against rust and matches the visual style of performance engines.
• Precision‑machined washers distribute load evenly, preventing deformation and extending joint life.
• Backed by ARP’s lifetime technical support and warranty, ensuring reliable after‑sales service.

FAQ

Can these bolts be used as replacements for OEM engine bolts?

Yes, the ARP 640‑0515 bolts meet or exceed OEM specifications for strength and thread dimensions, making them suitable direct replacements for many factory‑installed fasteners.

What torque specifications should be applied to the ARP 640‑0515 bolts?

ARP recommends a torque range of 70‑80 ft‑lb for the 1/4‑20 Grade 8 bolts when used with a washer. Always consult the specific vehicle service manual for exact values.

Are the bolts compatible with aluminum components?

The stainless‑steel construction and black oxide coating are designed to minimize galvanic corrosion, so the bolts can be safely used with aluminum brackets and housings when proper torque and anti‑seize are applied.

How should I store the bolt set to maintain its condition?

Keep the bolts in their original packaging or a dry, sealed container away from moisture and extreme temperatures. Avoid exposing the black oxide finish to abrasive cleaning agents.