SUPERTECH exhaust valve stem seals Opel X20XEV Z20LET

Opel engines concerned

These seals fit the 6 mm stem exhaust 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 serve in the Opel Astra F and G, Calibra, Omega B, Vectra A and B, Zafira A OPC and Speedster, the matching Vauxhall models and VX220, the Holden Astra, Calibra and Vectra and the Chevrolet Astra 2.0.

The engine has 8 exhaust valves, two per cylinder. The original seal surrounds the guide and meters the oil that lubricates the stem; GM supplies it as 90410741 (Opel 6 42 533), identical for the X20XEV and the Z20LET.

SUPERTECH exhaust valve stem seals

On the exhaust of the X20XEV, and even more of the Z20LET whose hot gases rush to the turbo, each stem seal takes severe heat. Once hardened or nicked, it lets oil reach the chamber through the 8 stems: the level needs topping up, a blue trail comes out of the tailpipe and carbon settles on valves and ports. Still, a little oil must pass to protect stem and guide.

For the exhaust, SUPERTECH moulds the seal in Viton (FKM): this compound was picked for long service next to the 8 exhaust valves of the 2.0 16V; SUPERTECH credits this material with handling the highest temperatures and rates it at 204 °C (400 °F) continuous. It sits on an 8.8 mm OD guide around a 6 mm stem. With 8 pieces, the set covers the full exhaust of an X20XEV or Z20LET; the polyacrylate (ACM) inlet seal is offered separately.

Stem seal technical specifications

Stem seal installation

Technical guide

The brand offered

SUPERTECH of San Jose, California, has spent 30-plus years designing racing valvetrain parts, valves and springs as well as guides and stem seals. Each new design begins as a finite element study, then gets approved by known tuners in drag racing, rally and circuit use.

Why two different materials?

On the X20XEV and Z20LET, the 8 inlet and 8 exhaust seals share the same size, yet the 2.0 16V exhaust valve gets noticeably hotter. SUPERTECH thus gives the tougher Viton (FKM) VS-VBM6-E to the exhaust and leaves polyacrylate (ACM) VS-VBM6-I to the inlet.

When valve stem seals must be replaced

• Oil use, blue trail at the tailpipe
• 2.0 16V head stripped for repair
• Valve guides changed
• Stronger valves or springs fitted

Vehicle compatibility

OPEL

VAUXHALL

HOLDEN

CHEVROLET

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

Remember the inlet valve stem seals

The X20XEV or Z20LET inlet wears at the same rate: change its 8 seals during the same strip-down. SUPERTECH offers this set: