BMW M20 Engine ARP Head Stud Kit - E30 325i, E34 525i

Virtually every top professional BMW engine builder relies on ARP Pro Series head studs. ARP uses a premium grade 8740 alloy that is rated far superior to "aircraft" quality. Each stud is heat-treated to 200,000 psi, ensuring complete heat penetration. ARP studs are threaded after heat-treat, which gives them 1000% (that's ten times!) better fatigue strength than studs threaded prior to heat-treat. Threading the studs after heat-treating is more difficult and costly (as it's harder on tooling) but the results are well worth the effort. These simply are the best head studs we've found and we highly recommend them in both racing and forced induction applications. Due to the additional clamping force between the head and block, these are IDEAL for turbocharged engines.

Converting from the factory BMW head bolts to head studs makes it much easier to assemble an engine, especially a racing powerplant which must be serviced frequently (and quickly!), and also ensures proper alignment of the head and gasket. Head studs also provide more accurate and consistent torque loading. Here's why: 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 head stud should be installed in a "relaxed" mode -- never crank it in tightly using a jammed nut. If everything is right, the stud should be installed finger tight. Then, when applying torque to the nut, the stud will stretch only on the vertical axis. An information sheet is provided with each set.

ARP is a company that prides itself on performance and durability, no matter the application. Offering the finest engine hardware money can buy is the driving initiative at ARP and this is evidenced by the staggering amount of satisfied customers and race teams the world over.​

This item fits the following BMWs:
1985-1991 E30 BMW 325e 325es 325i 325ic 325is 325ix
1989-1990 E34 BMW 525i