ARP Head Studs for EJ20/EJ25 (WRX and STI)

On many street-driven vehicles, where master cylinders and other items protrude into the engine compartment, it's necessary to use head bolts so that the cylinder heads can be removed with the engine in the car. For most applications, however, studs are recommended. And for good reason. Using studs will make it much easier to assemble an engine (especially a racing powerplant which must be serviced frequently and quickly!) with the cylinder head and gasket assured of proper alignment. 

Studs also provide more accurate and consistent torque loading. When you use bolts to secure the head, the fastener is actually being twisted while it's being torqued to the proper reading. Accordingly, the bolt is reacting to two different forces simultaneously. A stud should be installed in a relaxed mode and cranked in tightly using a jammed nut.