SUPERTECH inlet valve stem seals BMW MINI B46 B48

BMW and MINI engines concerned

This set fits the inlet side of the transverse 2.0-litre modular B46 and B48 four-cylinders with 5 mm valve stems: BMW 1 Series (F40, F70), 2 Series Active Tourer, Gran Tourer and Gran Coupé, X1 and X2, plus the MINI Cooper S, John Cooper Works, Clubman and Countryman, from 2013 onwards, codes B46A20A, B46A20B and B48A20A, B, E, F, H, P and S.

The four-cylinder has eight inlet valves. On the B48, BMW fits seal 11 34 0 038 719 from the factory; it surrounds the guide and meters the oil reaching the stem.

SUPERTECH inlet valve stem seals

On a turbocharged B48, the inlet stem seal holds back the oil in the upper head while letting the 5 mm stem receive just what it needs. With age, heat and boost cycles it stiffens and leaks: oil enters past the valves, top-ups become frequent, blue smoke shows at start-up or on the throttle, and carbon builds on the direct-injection inlet valves.

SUPERTECH makes this inlet seal in Viton (FKM), an elastomer with strong heat resistance, for a 5 mm stem. The 8 pieces cover every B46 or B48 inlet valve, one each; the exhaust, with 6 mm stems, takes its own Viton seal, sold separately.

Stem seal technical specifications

Stem seal installation

Technical guide

The brand offered

Racing valves, springs, guides and seals from SUPERTECH have come out of its San Jose, California workshops for more than 30 years. Every batch passes ultrasound, laser and radiography checks, with development led alongside top-level tuners.

Inlet or exhaust?

On these modular engines SUPERTECH uses Viton (FKM) on both sides; only the sizes change: VSI-BM50-I for the 5 mm inlet stem, VSI-BM60-E for the 6 mm exhaust stem, so the two seals are not interchangeable. The brand rates Viton at 204 °C (400 °F) continuous, a useful margin near turbo-heated valves. Eight seals on each side of the head.

When valve stem seals must be replaced

• Oil consumption and blue smoke on the B46 or B48
• Cylinder head off for a full overhaul
• Valve guides replaced
• Stronger valves or springs to be fitted

Vehicle compatibility

BMW

MINI

OEM part number (BMW inlet stem seal): 11 34 0 038 719 (B48)

Remember the exhaust valve stem seals

Exhaust seals age under exactly the same heat: renew them during that same job. For the B46 and B48, SUPERTECH offers: