Reinforced ARP cylinder head bolts/studs MINI W10B16 W11B16

The MINI engines concerned

The W10B16 and W11B16 are the 1.6-litre (1,598 cm³) inline four-cylinder petrol engines of the first generation of the modern MINI, built from 2001 to 2008. The naturally aspirated W10 powers the One and Cooper (R50) and their convertibles (R52); the supercharged W11 is fitted to the Cooper S (R53), the Works and John Cooper Works versions, and the Cooper S convertible (R52).

As standard, the cylinder head is held by ten main M10 bolts, 150 mm long (part number 07 13 1 487 226), plus two M8 bolts. The main bolts are tightened to 40 Nm then 90°, the two M8 bolts to 28 Nm. This angle tightening stretches the main bolts permanently.

Reinforced ARP cylinder head bolts and studs

Cylinder head fasteners work constantly: they hold the head tight against the block, crush the gasket to the right value and hold back the push of the gases at every combustion. If they lose even a little tension, the gasket starts to leak.

Two ARP kits are available for these engines. The 201-4301 stud kit, with 10 studs in 8740 and 12-point nuts, is fitted in the order set by its instruction sheet: the studs are first screwed hand tight into the block, the head is then installed, and the nuts are torqued, which gives a higher preload. The 206-3601 bolt kit, made up of 10 bolts in 8740 with 12-point heads, is fitted like the original fasteners: head in place, bolts torqued in the manufacturer's sequence. 8740 is a chrome-molybdenum steel, rated by ARP at 190,000 psi tensile strength. As a reference point, an engine's standard fasteners mostly belong to property classes 10.9 and 12.9, with a minimum tensile strength between 150,800 and 176,900 psi. In M10 x 1.5, the 8740 studs hold up to 500 hp on this four-cylinder engine (calculated estimate). On this four-cylinder engine, the limit of the 8740 bolts in M10 x 1.5 lies at 500 hp (calculated estimate).

Technical specifications

Tightening torque

201-4301 studs: no torque is applied to the studs as they go into the block: they are screwed in by hand. The instruction sheet leaves the option of thread locker to mount them permanently, provided tightening is done before the product hardens.

206-3601 bolts: a thread that opens into the cooling circuit receives ARP thread sealer, a blind hole receives ARP Ultra-Torque lubricant. Each washer is fitted with its chamfer facing the bolt head.

Final tightening is done in three successive stages, following the manufacturer's tightening sequence; these torque figures only hold with ARP assembly lubricant on the threads and under the nuts or bolt heads.

The instruction sheet also calls for ARP lubricant on the washers.

The tightening values above come from ARP instruction sheets 201-4301 (studs) and 206-3601 (bolts), in the revision current at the date of publication. If a sheet has been revised since, only the official version is authoritative, and it details the whole fitting procedure and the tightening sequence. Read the ARP 201-4301 instruction sheet ; Read the ARP 206-3601 instruction sheet

Technical guide

To obtain the intended preload, ARP assembly grease must be present on the threads and under the nuts or bolt heads: the torque figures in the table are established with it.

The ARP brand

Founded in the early 1970s by Gary Holzapfel, who came from the aerospace industry, ARP (Automotive Racing Products) set itself the mission of eliminating engine failures caused by inadequate fasteners in competition. Its thousands of parts are designed and produced in California, in several material grades depending on the application.

Advantages over the original bolts

Criterion	Original head bolts	Reinforced ARP studs	Reinforced ARP bolts
Tightening method	Torque then angle (40 Nm + 90°)	Torque only, in 3 stages	Torque only, in 3 stages
Block threads	Stressed at every tightening	Preserved (stud fitted hand tight)	Stressed at every tightening

When to upgrade the cylinder head fasteners

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

• Higher boost pressure on the supercharged engine, or forced induction added to the naturally aspirated engine
• 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: 07 13 1 487 226

Why is it the most cost-effective solution?

The original head bolts, tightened to torque then angle, remain permanently stretched. Stronger, the ARP 8740 fasteners withstand a much higher combustion pressure, supercharging 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

To get the most out of reinforced fasteners, pair them with a head gasket that withstands the same pressure. Here is the gasket we offer for this engine: