SUPERTECH exhaust valve stem seals 7 mm Nissan RB26DETT TB48DE

Nissan engines concerned

This set of 12 dresses the 7 mm stem exhaust valves of two Nissan 24-valve six-cylinders: the twin-turbo RB26DETT of the R32, R33 and R34 Skyline GT-R and the Stagea 260RS, and the 4.8-litre TB48DE of the Y61 and Y62 Patrol.

The exhaust of these engines has 12 valves, two per cylinder. The original seal sits on the guide and holds oil back without starving the stem; on the RB26DETT Nissan lists it as 13207-84A00 (NDK) or 13207-D4201 (NOK).

SUPERTECH exhaust valve stem seals

Mounted on the guide of a valve that discharges the hottest gases, the exhaust seal faces the harshest thermal load in the head. As the rubber ages, shrinks or splits, it stops holding back the lubricant, which flows toward the cylinder and is consumed: falling oil level, bluish smoke, fouled valves and manifold. A tiny amount must still lubricate the stem, or guide and stem wear early.

This SUPERTECH set is moulded in Viton (FKM), a fluoroelastomer the brand highlights for strong heat, rated at 204 °C (400 °F) continuous, which suits it to exhaust valves. Its dimensions match a 7 mm stem and an 11 mm outside diameter guide. Twelve pieces cover the whole six-cylinder exhaust; the 6 mm polyacrylate (ACM) intake seals are ordered separately.

Stem seal technical specifications

Stem seal installation

Technical guide

The brand offered

A valvetrain component maker based in San Jose, on the California bay, SUPERTECH has served motorsport for more than 30 years with valves, springs, guides and seals. Its developments rely on finite element modelling and on track testing carried out with tuners.

Why two different materials?

Unusually, the stem size differs between sides: 6 mm on the intake, served by VS-N6I polyacrylate (ACM), and 7 mm on the exhaust, served by the more heat-tolerant VS-N7E Viton (FKM), since the exhaust valve runs hotter. Both the RB26DETT and TB48DE need 12 exhaust seals each.

When valve stem seals must be replaced

• Repeated oil top-ups, bluish smoke
• Head opened for overhaul
• New valve guides installed
• Uprated valves or springs going on

Vehicle compatibility

Nissan

OEM part number (Nissan RB26DETT stem seals): 13207-84A00 (NDK) or 13207-D4201 (NOK).

Remember the inlet valve stem seals

The RB26DETT intake uses 6 mm seals that age the same way; replace them at the same time. SUPERTECH sells them for this engine: