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ARP Hardware & Fasteners

ARP Hardware & Fasteners

ARP Hardware and Fasteners for Aircooled and Watercooled Porsche Engines

ARP Fasteners Porsche Cylinder Head Stud Kit

ARP Fasteners is the world leader in automotive fastener technology. ARP Fasteners manufactures hardware including cylinder head studs, case bolts, and connecting rod bolts for Porsche engines in the USA at their Ventura, CA facility. LN Engineering is proud to have both used and recommended APR fasteners exclusively in all Porsche engine rebuilds since 2002.

ARP started applying technology to race fastener design and manufacturing in 1968 and was the first company to design and engineer fasteners specifically for racing. They developed many patented process for manufacturing high strength fasteners from very strong materials and have continued to improve their processes and quality control with manufacturing operations that are ISO 9001 and AS9100 registered. These registrations represent ARP's unwavering dedication to producing quality fasteners, continually improving our quality management system and delivering total customer satisfaction. There is no another company in the world that is as focused on building superior quality fasteners for all forms of racing and non-racing applications as Automotive Racing Products.

ARP uses a variety of materials for their fasteners, including:
 

  • Chromoly: Chromoly is a type of alloy steel that is known for its high strength, durability, and resistance to wear and tear. It is often used in applications that require high strength and durability, such as in engine and suspension components.
  • Stainless Steel: Stainless steel is a type of steel that is known for its resistance to corrosion and rust. It is often used in applications that require resistance to corrosion, such as in exhaust systems and other areas where the fastener is exposed to the elements.
  • Custom Age 625+: This is a proprietary alloy from ARP made of nickel, chrome and molybdenum and is known for its high strength and resistance to corrosion. This material is used for extreme high-performance and high-stress applications such as in engines, suspension and more.
  • Pro Series: This is a line of fasteners from ARP that are made from a proprietary alloy that is designed for high-performance and high-stress applications. These fasteners are known for their strength, durability, and resistance to wear and tear.
  • Titanium: Titanium is a lightweight and strong metal that is known for its corrosion resistance, high strength-to-weight ratio, and resistance to wear and tear. It is often used in applications that require a combination of strength and weight savings, such as in aerospace and racing applications.

Each material has its own unique properties and is used in different applications and environments, so it's important to select the right material for the specific application. It's worth noting that the selection of fasteners depends on the application and the performance required from the engine and it's always good to consult with an expert or a mechanic before making a decision.

Some of the most popular ARP fasteners for Porsche engines include:
 

  • Porsche Cylinder Head Studs: ARP's head studs are popular for Porsche engines, as they provide increased clamping force, which helps to improve engine performance and reduce the risk of cylinder head leaks or broken head studs common to Dilivar head studs.
  • Porsche Case and Through Bolts: Case and Through Bolts from ARP are popular for Porsche engines, as they provide increased clamping force, which helps to improve engine performance and reduce the risk of case shuffling and main bearing failure or fretting that can occur in Porsche engines making more horsepower than stock, that are tracked, or will see sustained high rpm operation.
  • Porsche Connecting Rod Bolts: ARP's rod bolts are popular for Porsche engines, as they provide increased clamping force and improved reliability over the factory fasteners which can stretch and fail resulting in spun rod bearing or connecting rod failure.
  • Porsche Flywheel bolts: ARP's flywheel bolts are popular for Porsche engines, as they provide increased clamping force and improved reliability over the factory Porsche fasteners.

LN Engineering recommends ARP fasteners and its Nickies Cylinders were developed for and tested with ARP Head Studs in the ARP 2000 and Custom Age 625 alloy. ARP manufactures fasteners from a wide assortment of materials ranging from popular stainless steel and 8740 chrome moly to exotic alloys to meet the application requirements for each fastener. The ARP2000 material used to make ARP head studs, case bolts, and connecting rod bolts is about 33% stronger than the stock material, with a 220,000psi tensile strength and improved fatigue characteristics. Our Porsche 356 and 912 ARP head studs are available exclusively through LN Engineering utilize the ARP2000 material. The ARP Porsche 911 head studs have a 265,000+ psi tensile strength and use ARP Custom Age 625+. All ARP studs have been designed and tested for use with Nickies™ Cylinders!

The reason for offering replacement studs stems from the fact that our testing found that no available head stud was compatible with our Nickies™ or any aluminum cylinders for that matter, with exception of the 911 models equipped with aluminum cylinders from the factory. In most cases, the factory head studs are unable to perform satisfactorily under the increased expansion of an aluminum cylinder, in most cases leading to head leaks and fastener fatigue.

On 911 models, certain engines came fitted with Dilivar head studs, which were designed to match the expansion of the cylinders, but also suffered from hydrogen embrittlement, which is a condition that results from the accumulation of hydrogen gas in the atomic structure of the metal. This gas flows to the point of high stress (stress risers) and causes microscopic cracks. The hydrogen then flows to the “new” crack tip and causes it to crack further. In this way the crack moves across the part, because the crack-tip IS the stress riser. Finally the crack gets so large that the section is not large enough to support the load. Hydrogen embrittlement can take place without tensile stress. ARP® employs a baking process that purges hydrogen gas from the steel, eliminating this problem.

Like with Porsche's Dilivar cylinder head studs, the stock Porsche connecting rod bolts should be replaced and upgraded whenever you are rebuilding your Porsche engines as they can stretch and fail. ARP offers upgraded rod bolts for the stock Porsche connecting rods that are superior to replacement fasteners offered by Porsche.

ARP's head studs are required for use with Nickies cylinders. ARP or equivalent upgraded head studs can be used where the use of OE head studs are not recommended.

Many of ARP's fasteners replace the original factory Porsche torque to yield (TTY) hardware and are proven to provide a lifetime of reliability and performance.

For best results, follow the instructions provided with your new ARP fasteners, as they may differ from factory specifications or installation procedures and proper installation is critical for any fastener. ARP offers a detailed Fastener Installation Overview that goes over the difference between the three generally accepted methods employed to determine how much tension is exerted on a fastener.

For applications where ARP fasteners are not available or desired, we stock and recommend Raceware fasteners for Porsche engines.
 

Porsche Torque-to-Yield (TTY) Fasteners VS ARP Fasteners

Torque-to-yield (TTY) fasteners are a type of fastener that is designed to stretch a specific amount when tightened, creating a clamping force that holds the components together. They work by being tightened to a specific torque value, which causes the fastener to stretch and deform slightly. This stretching creates a pre-load or tension in the fastener which helps to keep the components securely fastened together. The TTY fasteners are typically used in engines and other high-performance applications where a consistent and precise clamping force is required. They are designed to stretch a specific amount when tightened, which allows them to create a consistent and reliable clamping force.

When installing TTY fasteners, it is important to use the correct torque specifications and to not reuse them after they have been stretched, as they will not be able to maintain the same clamping force. Also, TTY fasteners are one-time use fasteners and are not meant to be reused as they lose their elasticity after being stretched once. It is important to note that TTY fasteners are typically used in applications where the clamping force needs to be consistent and precise, and are not meant to be reused after they have been stretched.

ARP (Automotive Racing Products) fasteners are often considered to be a better choice than factory torque-to-yield (TTY) fasteners for several reasons:
 

  • Increased strength: ARP fasteners are made from a stronger material, such as aircraft-grade alloy steel, which allows them to withstand greater loads and stresses than factory TTY fasteners.
  • Improved reliability: ARP fasteners are designed to have a tighter tolerance and better fit than factory TTY fasteners, which reduces the chance of failure and improves overall reliability.
  • Greater durability: ARP fasteners are designed to last longer than factory TTY fasteners, which means they will need to be replaced less often, saving time and money in the long run.
  • Greater clamping force: ARP fasteners have a greater clamping force than factory TTY fasteners, which allows them to hold the engine components together more securely.
  • Reusability: Factory TTY fasteners are designed to stretch and deform, which means they must be replaced after a single use. ARP fasteners are designed to be reusable, which allows them to be used multiple times without any degradation of performance.
  • Customizable: Many of the ARP fasteners are customizable as per the requirement of the engine and the performance it is expected to deliver.

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