Reinforced ARP cylinder head studs BMW Toyota B58B30

The engine concerned

The B58B30 is BMW's 3.0-litre turbocharged inline six-cylinder petrol engine (2,998 cm³, 82 mm bore, 94.6 mm stroke), in production since 2015. It powers many BMW models, from the M140i to the 7 and 8 Series, including the X3, X4, X5, X6, X7 and Z4, as well as the Toyota GR Supra from 2019.

As standard, the cylinder head is held by M11 bolts, 188 mm long (part number 11 12 8 644 674). The manufacturer specifies tightening to torque, followed by an angle.

Reinforced ARP cylinder head studs

Every combustion cycle pushes the cylinder head upwards. The head fasteners resist it by keeping a constant clamping pressure on the gasket; if that pressure drops, the seal is no longer guaranteed.

Four ARP kits of 14 studs with 12-point nuts, M11 diameter, are offered: the 201-4701 (BMW) and 203-4705 (Toyota GR Supra) in ARP2000, the 401-4701 (BMW) and 203-4706 (Toyota GR Supra) in CA625+. According to the instruction sheets, the cylinder head and its gasket are fitted first; the studs are screwed into the block afterwards. These ARP2000 studs in M11 are calculated to handle up to 1,000 hp on this six-cylinder engine (calculated estimate). In M11, the CA625+ studs hold up to 1,200 hp on this six-cylinder engine (calculated estimate).

Technical specifications

Tightening torque

For all four kits: the studs are fitted by hand into the block threads, without a torque wrench. The instruction sheet makes no provision for thread locker. According to ARP, some installers apply a blue one to the block-end thread only; never on the nuts or together with ARP grease, and tightening must be completed before it sets.

Follow the tightening sequence recommended by the manufacturer and bring to torque in three stages; the stated values assume ARP lubricant on the threads and under the nuts.

The washers go on dry, clean on both faces, onto degreased cylinder head seats; an oil film at this point would distort the tightening.

These torque figures are taken from ARP instruction sheets 201-4701, 401-4701, 203-4705 and 203-4706, in the revision current on the day of publication. In the event of any difference, the official instruction sheet applies; it also describes the full procedure and the tightening sequence. Read the ARP 201-4701 instruction sheet; Read the ARP 401-4701 instruction sheet; Read the ARP 203-4705 instruction sheet; Read the ARP 203-4706 instruction sheet

Technical guide

All torque values on this page are given with ARP assembly grease on the threads and under the nuts; another lubricant would make them wrong.

The available grades

The ARP brand

ARP (Automotive Racing Products) was born in the early 1970s from the initiative of Gary Holzapfel, an engineer from the aerospace industry, determined to eliminate engine failures caused by weak fasteners in motorsport. The company designs and manufactures thousands of parts in California, in several material grades suited to each use.

Advantages over the original bolts

Criterion	Original head bolts	Reinforced ARP studs
Tightening	Torque then angle	Torque only, in three stages
Block threads	Stressed at every tightening	Preserved (studs fitted hand tight)

When studs become necessary

The original fasteners are sized for the engine as it leaves the factory. They need to be reinforced when:

• B58B30: higher boost pressure, through an engine remap or a turbo change
• The compression ratio rises as the build progresses
• The original gasket is replaced by a reinforced MLS gasket, which requires a high and uniform preload
• The engine has already suffered a lifted head or a gasket leak
• Competition use imposes severe heat cycles and regular head removals

Vehicle compatibility

OEM reference: 11 12 8 644 674

Why is it the most cost-effective solution?

The original head bolts, tightened to torque then angle, remain permanently stretched. Stronger, the ARP2000 and CA625+ fasteners withstand a much higher combustion pressure, turbo included: they limit the risk of gasket leaks or breakage, and so avoid a rebuild far more expensive than the kit.

Consider a reinforced head gasket

Reinforced fasteners and the head gasket work together: the gasket must hold the same pressure as the fasteners. The matching gasket for this engine: