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ARP Head Studs & Thru-Bolts

The proprietary ARP materials used to make our VW and Porsche head studs, thru-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 model as well as VW Type 1 and 4 head studs are available exclusively through LN Engineering. The ARP 911 head studs have a 265,000+ psi tensile strength. 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. Used or old-style Dilivar head studs should be replaced and are not recommended for use with Nickies™ cylinders. Later 993TT model dilivar are also compatible with Nickies™ cylinders. ARP's head studs are proven and tested for a lifetime of reliability and performance.

Use of ARP fasteners in your Porsche or VW engine will ensure that your engine will be assembled with the most accurate and even clamping load possible, and will maintain that spec for prolonged periods of operation.

Our VW Type 1 ARP head studs are 10mm - we do not offer an 8mm stud. The VW Type 4 ARP head stud is a direct replacement for the factory head stud, as is the Porsche 356 and 912 model ARP head studs. Where applicable, 12-pt hardware, including nuts, washers, and ARP lube are included. Our Porsche 356 and 912 model ARP head studs are designed to be used with factory fasteners.

We also offer a wide array of case through bolts, connecting rod bolts, and other fasteners manufactured by ARP for Porsche and VW models.

2009 Pricing Schedule*
*with qualifying Nickies purchase

Contact us at 815-472-2939 or info@LNengineering.com to bring your “tried and true" Aircooled engine to the new standard of precision performance!

All LN Engineering Products are Proudly 100% Made in the USA!