Reinforced exhaust valves VW Touareg Phaeton 4.2 V8 40V AXQ BGH BGJ

Volkswagen engines covered

Volkswagen fitted the group's 4.2 litre, 40-valve V8 to the first-generation Touareg (AXQ code, 310 hp) and then to the Phaeton 4motion saloon (BGH and BGJ codes, 335 hp).

This engine carries 16 exhaust valves, original part number 077 109 611 S. In an SUV that tows or a large saloon weighing more than two tonnes, they stay exposed to scorching exhaust gases for long periods.

SUPERTECH reinforced exhaust valves

The metal of an exhaust valve head rises to 760 to 870 °C on an engine without forced induction, and passes 1,000 °C once a turbo or supercharger is added. The seat removes nearly 75 % of that heat, the guide about 20 %. An EV8 family steel withstands 550 MPa at 600 °C, but only 300 MPa at 800 °C: the head fatigues and distorts, and sealing deteriorates.

Made from Inconel, a nickel-based superalloy, the AEVI-1206S-16 holds 860 MPa at 730 °C and 554 MPa at 815 °C: around 800 °C, its strength exceeds that of an EV8 steel by roughly 85 %. A single groove holds the valve in its collets.

Its head measures 30.9 mm, 1 mm more than the standard size: burnt gases leave the cylinder faster, which helps filling. This size requires exhaust seats machined accordingly.

Exhaust valve technical specifications

AEVI-1206S: 30.9 mm head (+1 mm), 5.94 mm stem, 94.8 mm length, Inconel, single groove.

Valve fitting

Plan for KPR-6S-7 single-groove collets, suited to this stem: the original collets are not suitable.

Have the 16 exhaust seats machined for the 30.9 mm head before fitting the valves.

Use the strip-down to change the exhaust valve stem seals, and fit all 16 valves from one set.

Technical guide

Our brand

SUPERTECH Performance has been designing valvetrain parts for racing in California for more than thirty years: valves, springs and guides. For the Volkswagen 4.2 litre V8, the brand supplies a single-groove Inconel exhaust valve, 1 mm oversize.

How to choose

These engines have only one version:

When reinforced valves become necessary

• Fitting a turbo or supercharger (Inconel version recommended)
• Heavy towing or long climbs under load
• Higher lift camshafts
• Cylinder heads rebuilt after burnt or distorted exhaust valves

Vehicle compatibility

OEM part number (exhaust valve): 077 109 611 S

Don't forget the inlet valves

Once the V8 cylinder heads are off, remember to change the inlet valves and the valve stem seals too.