SUPERTECH inlet valve stem seals Audi S4 B6 B7 4.2 40V BHF

Audi engines concerned

This set fits the 6 mm stem inlet valves of the Audi 4.2 V8 40-valve BHF engine, used in the B6 and B7 generation S4 saloon, Avant and Cabriolet, built from 2003 to 2009 with 344 hp.

With five valves per cylinder, three inlet and two exhaust, this V8 has 24 inlet valves. The original seal caps the guide and holds oil back along the stem; Audi lists it as 036 109 675 A, 40 per engine, inlet and exhaust combined.

SUPERTECH inlet valve stem seals

On a valve stem, the seal should only let a thin film of oil through, the one that lubricates the stem in its guide: deprived of oil, stem and guide get damaged. Once age or heat hardens it, oil slips towards the chamber: the engine uses oil, smokes blue after a start or a long idle, and fouls valves and plugs.

At SUPERTECH, the inlet takes a seal moulded in a fine rubber, polyacrylate (ACM), fitted on a guide of 8.8 mm outside diameter around a 6 mm stem. The set of 24 covers both cylinder heads of the V8; the hotter exhaust has its own seals in a high-temperature compound, offered separately.

Stem seal technical specifications

Stem seal installation

Technical guide

The brand offered

Born in San Jose, California, SUPERTECH has designed racing engine valvetrains for more than 30 years, valves and stem seals included. Every batch goes through ultrasonic, X-ray and laser inspection, then is fine-tuned with renowned engine builders.

Inlet or exhaust?

Same dimensions, different materials: the inlet uses polyacrylate (ACM) VS-VBM6-I, the exhaust Viton (FKM) VS-VBM6-E, far better suited to the hotter exhaust valves. According to SUPERTECH, polyacrylate withstands 177 °C (350 °F) and Viton 204 °C (400 °F) in continuous use. The 40-valve V8 needs 24 inlet seals and 16 exhaust seals.

When valve stem seals must be replaced

• Oil consumption, blue smoke after a cold start or long idle
• Cylinder heads removed for an overhaul
• Valve guides to be renewed
• Fitting uprated valves or springs

Vehicle compatibility

Audi

OEM part number (VAG stem seal): 036 109 675 A (BHF)

Remember the exhaust valve stem seals

On the exhaust side, seals are renewed during the same job as the inlet ones. SUPERTECH supplies the seals for this V8: