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Weistec has exclusively partnered with ARP, the top name in performance engine hardware. Head studs are used to fasten the heads to the block in place of the factory head bolts. The connection between the cylinder heads and the block is a complex part of the engine. Coolant and oil flow back and forth between the block and the cylinder heads. The head gasket keeps the coolant, oil, and air charge in the cylinders separate from each other with the help of pressure generated by the head bolts. The factory head bolts are "torque to yield" meaning that when installed, they are tightened to the point where they permanently stretch. There have been stock M156 oil leak issues resulting from a poor connection between the cylinder heads and the block which in part can be attributed to the head bolts.
With 260,000+PSI of tensile strength, our ARP 625+ head studs are able to hold down the heads with far greater pressure than the factory head bolts, without permanent stretching. The result is a more reliable performance engine that will not be susceptible to leaks between the heads and block. Quality head studs are among the top items in the list of parts that allow an engine to reliably reach high power levels.
260,000 psi Tensile Strength
255,000 psi Yield Strength
Complete replacement of factory head bolts
Improved Head to Block connection eliminating leaks
Reusable, unlike the factory bolts which are "one time use"
Unless otherwise stated, some Weistec Engineering performance upgrades are sold for race car use only.