Reinforced ARP cylinder head bolts and studs Audi A3 S3 TT A4 SEAT Leon Ibiza VW Golf 4 1.8T AEB AGU AMK BAM

The engines concerned

The 1.8-litre 20-valve turbo engine (1,781 cc) of the Volkswagen Audi group is an inline four-cylinder petrol engine built from 1995 to 2009 under the codes AEB, AGU, AMK, APX, APY, AWP, BAM and others. It powers in particular the Audi A3 and S3 8L, the Audi TT 8N, the Audi A4 B5, B6 and B7, the SEAT Leon and Ibiza Cupra, the VW Golf 4 and GTI, the New Beetle and the Polo GTI.

As original equipment, the cylinder head is held by Polydrive-head cylinder head bolts (part number 06A 103 384 C, sold as a set), which stretch as they are tightened. For the 1997 to 2003 model years they are tightened to 40 Nm, then 60 Nm, then twice through 90°, using new bolts.

Reinforced ARP cylinder head bolts and 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.

Six ARP kits exist for this engine. The 204-4101 and 204-4102 studs, in M11 x 1.5 thread, are designated by ARP for the early AEB; the 204-4103 and 204-4104 studs and the 204-3901 and 204-3902 bolts are in M10 x 1.5 thread. Each kit comprises 10 ARP2000 pieces; the studs come with 12-point nuts, the bolts have a 12-point head. According to ARP's designation, parts 204-4102, 204-4104 and 204-3902 are supplied with an installation tool, and parts 204-4101, 204-4103 and 204-3901 without a tool. Before ordering, check the thread of the block: M11 or M10.

The studs are fitted in the order set by their instruction sheet: first screwed into the block by hand, then the cylinder head is fitted, then the lubricated nuts are tightened to torque in three equal passes. The bolt instruction sheet asks you to fit the gasket and then the cylinder head, lubricate the threads and the underside of the head, then tighten in three passes.

The ARP2000 range relies on an alloy steel developed by ARP: after heat treatment it reaches 220,000 psi tensile strength, and the threads are rolled afterwards. As standard bolts generally belong to classes 10.9 and 12.9, i.e. 150,800 to 176,900 psi minimum, ARP2000 exceeds them by 24 to 46 %.

These ARP2000 studs in M11 x 1.5 are calculated to handle up to 700 hp on this four-cylinder engine (calculated estimate). In M10 x 1.5, the ARP2000 studs hold up to 600 hp on this four-cylinder engine (calculated estimate). On this four-cylinder engine, the limit of the ARP2000 bolts in M10 x 1.5 lies at 600 hp (calculated estimate).

Technical specifications

Tightening torque

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.

M11 studs (204-4101 and 204-4102): the instruction sheet asks you to clean the block threads, with the ARP 912-0005 thread chaser (M11 x 1.5) if needed. ARP thread sealer is only used if the studs open into a water jacket.

M10 studs (204-4103 and 204-4104): same instructions, with the ARP 912-0003 thread chaser (M10 x 1.5).

204-3901 and 204-3902 bolts: clean the block threads, with the ARP 912-0003 thread chaser (M10 x 1.5) if needed, fit the gasket and then the cylinder head, lubricate the threads and the underside of the head with ARP Ultra-Torque lubricant, and screw the bolts in by hand before tightening.

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 or bolt heads.

The washers also receive ARP lubricant, as stated in the instruction sheet.

These torque figures are taken from ARP instruction sheets 204-4101 (kits 204-4101 and 204-4102), 204-4103 (kits 204-4103 and 204-4104) and 204-3901 (kits 204-3901 and 204-3902), in the revision in force on the day of publication. If there is any difference, the official sheet applies; it also describes the complete procedure and the tightening sequence. Read the ARP 204-4101 instruction sheet ; Read the ARP 204-4103 instruction sheet ; Read the ARP 204-3901 instruction sheet

Technical guide

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

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	ARP2000 studs	ARP2000 bolts
Tightening method	Torque then angle (40 Nm + 60 Nm + 90° + 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 original turbo, or a larger turbo with remapped engine management
• 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: 06A 103 384 C

Why is it the most cost-effective solution?

As standard, the head bolts are tightened to torque then angle and stretch permanently. Stronger, the ARP2000 fasteners stand up to a much higher combustion pressure, turbo included: they reduce the risk of gasket leaks or breakage, and therefore of a rebuild out of all proportion to the price of 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: