SUPERTECH inlet valve stem seals Opel X20XEV Z20LET

Opel engines concerned

This set fits the 6 mm stem inlet valves of the GM Ecotec 2.0 16V four-cylinders: the naturally aspirated 136 hp X20XEV and the 190 to 200 hp Z20LET turbo. They are found at Opel (Astra F and G, Calibra, Omega B, Vectra A and B, Zafira A OPC, Speedster), Vauxhall (Astra, Calibra, Cavalier, Omega, Vectra, Zafira, VX220), Holden (Astra, Calibra, Vectra) and in the Chevrolet Astra 2.0.

Each head carries 8 inlet valves, two per cylinder. The original seal caps the guide and only lets through the oil the stem needs; GM lists it as 90410741 (Opel 6 42 533) for the X20XEV and the Z20LET alike.

SUPERTECH inlet valve stem seals

On the X20XEV and Z20LET, the inlet seal meters oil tightly: a thin film for the 6 mm stem in its guide, nothing more. Over the years the heat of the 2.0 16V stiffens it until it gives way: falling oil level, a blue cloud on first start-up or after long idling, deposits on valves and plugs, even worse under Z20LET boost.

SUPERTECH makes this seal in a premium polyacrylate (ACM), sized for 8.8 mm OD guides and 6 mm stems. The batch of 8 covers the complete inlet side of an X20XEV or Z20LET; the hotter exhaust side takes a seal in another compound, which is sold separately.

Stem seal technical specifications

Stem seal installation

Technical guide

The brand offered

Born over 30 years ago in San Jose, California, SUPERTECH specialises in competition valvetrain, from valves and springs to guides and stem seals. Ultrasound, X-ray and laser measurement validate each part, which is then refined with top-tier engine tuners.

Inlet or exhaust?

The X20XEV and Z20LET take seals with common dimensions but in two different materials: polyacrylate (ACM) VS-VBM6-I for the inlet side, Viton (FKM) VS-VBM6-E on the noticeably hotter exhaust. According to SUPERTECH, polyacrylate resists 177 °C (350 °F) and Viton 204 °C (400 °F) in continuous use. A GM 2.0 16V needs 8 seals of each kind.

When valve stem seals must be replaced

• Falling oil level, blue cloud on X20XEV or Z20LET
• Valves out and cylinder head rebuilt
• Valve guides replaced
• Sturdier valves or springs being fitted

Vehicle compatibility

OPEL

VAUXHALL

HOLDEN

CHEVROLET

OEM part number (Opel stem seal): 90410741 (Opel 6 42 533; X20XEV, Z20LET)

Remember the exhaust valve stem seals

The exhaust ages alongside: replace its seals during the same strip-down. For the X20XEV and Z20LET, SUPERTECH offers this set: