Reinforced ARP main studs for Audi S4 RS4 B5 2.7T twin-turbo

The VAG engines concerned

This kit is made for the Volkswagen Group V6 twin-turbo of 2.7 litres and 30 valves (codes AGB, AZB, ASJ and AZR), fitted to the Audi S4 B5 and RS4 B5.

Reinforced ARP studs for main bearings

The bottom end rests on its main bearings: combustion after combustion, the loads coming from the connecting rods end up on them. Under this stress the main cap tries to move on its parting line, which eventually brinells the mating faces and distorts the bearing bore.

Here the original main cap fasteners give way to 11 mm ARP studs in ARP2000 steel, together with their nuts and the M8 side bolts of the kit. Each stud is screwed into the block by hand; the caps are then fitted, threads and nuts receive the ARP Ultra-Torque lubricant provided, and the nuts are torqued in three passes, in the manufacturer's sequence. Tightening becomes more uniform, preload rises and the block threads are no longer stressed by the turning of the bolt.

These fasteners are made from ARP2000, an ARP-specific alloy steel that reaches 220,000 psi tensile strength after heat treatment; the threads are rolled afterwards. Compared with classes 10.9 and 12.9 of the original fasteners, from 150,800 to 176,900 psi minimum tensile strength, the margin ranges from 24 to 46%. These ARP2000 studs in M11 x 1.5 take up to 2,300 hp on this twin-turbo V6 engine (calculated estimate).

Technical specifications

Tightening torque

The studs are screwed into the block by hand, with no torque. The ARP instruction sheet allows a thread locker of the blue Loctite type on the block end for a permanent installation, provided the nuts are fully tightened before it sets; never on the nuts, never with ARP grease.

The M8 side bolts of the kit are tightened to 27 Nm (20 ft-lb).

Follow the cap tightening sequence recommended by the manufacturer when bringing the nuts up to torque; the kit's instruction sheet details each step.

With stronger fasteners, the clamping force is no longer what it was originally: the size and roundness of the main bearing bores must be checked once installation is complete, and align honed if necessary with the final fasteners and lubricant.

Values taken from the ARP 204-5801 instruction sheet in force at the date of publication; the official instruction sheet prevails should any difference appear. Read the ARP 204-5801 instruction sheet

Technical guide

The torque figures given only apply with ARP assembly grease, never with engine oil.

The ARP brand

Founded in the early 1970s by Gary Holzapfel, who came from the aerospace industry, ARP (Automotive Racing Products) set out to prevent fastener-related engine failures in motorsport. Its thousands of part numbers are designed and manufactured in California, in materials chosen for each use.

Advantages over the original bolts

Criterion	Original main bolts	ARP studs
Tightening method	Bolt turned into the block	Nuts tightened progressively, in three passes
Block thread	Loaded by the turning bolt	Stud placed by hand, no torque load
Refitting the caps	Cap to be held while screwing	Cap positioned by the studs

When studs become necessary

• Turbocharged or supercharged engine, or boost raised beyond stock
• Build that increases engine speed or stroke
• Bottom end overhaul
• Caps that have moved or marked block threads
• Track or rally use with repeated loads

Vehicle compatibility

Why is it the most cost-effective solution?

On a 2.7 litre twin-turbo pushed beyond its original output, ARP studs in ARP2000 steel, stronger than the original fasteners, clamp the main caps more firmly and reduce the risk of bottom-end failure. Their cost stays reasonable next to the cost of rebuilding a crankshaft and a block.