ARP Head Stud Kit – BMW M50 2.5L Inline-6 | 12-Point | E34 / E36 | 201-4302

ARP 201-4302 cylinder head stud kit for the BMW M50B25 2.5L DOHC inline-6. Chrome moly 8740 alloy studs with 12-point nuts replace the OEM head bolts with a fastener system engineered for consistent, repeatable clamping force. The standard upgrade for any M50 build requiring reliable head gasket retention beyond OEM bolt capability. Ships fast across Canada and the US.

Head Studs vs OEM Head Bolts — Why It Matters on the M50

The BMW M50B25 uses torque-to-yield (TTY) OEM head bolts — single-use stretch bolts that are tightened to a specified angle beyond yield point to generate clamping force. TTY bolts work well for OEM power levels and OEM assembly conditions, but have limitations for performance builds:

• Single use: TTY bolts must be replaced every time the head is removed. On a performance build with multiple assembly iterations, this adds up quickly. ARP studs are reusable — clean, re-lubricate with ARP Ultra-Torque, and re-torque to spec.
• Torque inconsistency: When a bolt rotates into the block during torquing, thread friction adds an unknown variable to the torque reading. Studs are pre-installed and stationary — only the nut rotates during torquing, giving a clean, friction-consistent torque measurement and more accurate clamping force.
• Clamping force at elevated cylinder pressure: Boosted M50 builds (turbo or supercharged), high-compression NA builds, and high-revving applications generate cylinder pressures that exceed what OEM TTY bolt clamping force was designed for. ARP’s 8740 chrome moly alloy provides significantly higher tensile strength than OEM bolt material — maintaining the head-to-block seal under elevated thermal and mechanical loads.

BMW M50B25 Applications

The M50B25 is the 2.5L variant of BMW’s M50 DOHC inline-6 engine family, produced from 1990 to 1995. Primary applications covered by the ARP 201-4302:

• BMW E36 325i / 325is: The M50B25 was the standard engine in the E36 325i from 1992–1995 (before the M52 transition). A very common platform for turbo and performance builds in the BMW community.
• BMW E34 525i: The M50B25 powered the E34 525i from 1991–1995 — a popular track and touring car base.

The M50 is also the base architecture for the S50 motorsport engine used in European E36 M3 models — confirm S50 head bolt specification compatibility separately before applying this kit to an S50 application.

12-Point Hardware

ARP supplies 12-point (double hex) nuts with the 201-4302 kit. 12-point sockets engage at 30-degree intervals vs 60-degree for standard 6-point — allowing the socket to fit and turn in tighter locations where a 6-point socket cannot achieve full engagement. On the M50 cylinder head, where bolt access can be restricted by surrounding components, the 12-point hardware is a practical advantage during assembly.

ARP — The Fastener Standard

Automotive Racing Products (ARP) is the reference standard for performance engine fasteners. ARP’s 8740 chrome moly alloy is heat-treated to 190,000 PSI tensile strength — significantly beyond OEM fastener material. Every ARP stud is individually tested and serialised. The 201-4302 kit includes all studs, hardened washers, 12-point nuts, and ARP lubricant for installation.

M50B25 only — confirm engine code before ordering. Head must be lifted straight off studs during removal — confirm clearance. ARP Ultra-Torque lubricant required for accurate torque readings — included in kit. Professional engine assembly experience recommended.

Specifications

• Brand: ARP
• Part Number: 201-4302
• Type: Cylinder head stud kit
• Hardware: 12-point nuts, hardened washers
• Material: 8740 chrome moly alloy
• Application: BMW M50B25 — 2.5L DOHC inline-6 — E34 525i / E36 325i / 325is — 1991–1995
• Includes: Studs, hardened washers, 12-point nuts, ARP lubricant