Reinforced inlet valves NISSAN Skyline Laurel RB20DE RB20DET

NISSAN engines covered

The RB20 is Nissan's 2 litre straight six. Its RB20DE (naturally aspirated) and RB20DET (turbo) versions have twin overhead camshafts and 24 valves, from 155 to 224 hp, and power the Skyline R31 and R32, the Laurel C33 and C34 and the Cefiro A31.

Their 12 original inlet valves, Nissan 13201-58S11 on the RB20DE and 13201-59S11 on the RB20DET, work with hydraulic tappets and collets 13210-D4200. More boost, sharper cams or a higher rev limit expose them to more heat and impact.

SUPERTECH reinforced inlet valves

On every cycle the inlet valve opens the way for fresh air, closes back on its seat and slides in its guide, between 400 and 550 °C. In that range an ordinary chrome-silicon steel drops from 500 MPa at 500 °C to 250 MPa at 600 °C, 50 % less strength.

The SUPERTECH valves are black nitrided stainless: nitriding hardens the stem surface and limits wear in the guide. The stem is undercut below the head and the head is back cut, two machining steps that clear the air path.

Both sets have a 31.1 mm head, the +1 mm size: the flow area grows and the cylinder fills better, provided the 12 inlet seats are machined to that diameter.

Inlet valve technical specification

NIVN-1042-12: for heads with original hydraulic tappets, 4.5 mm stem tip.

NIVN-1042-SL-12: 16.8 mm longer, for a solid tappet conversion, 7.4 mm stem tip.

Fitting details

SUPERTECH pairs this engine with its machined and hardened KPR-6N-6-ST-24 collets, for a 6 mm stem, and its VS-N6I-12 inlet valve stem seals.

The 31.1 mm head requires the 12 inlet seats to be machined to its size before reassembly.

On a head converted to solid tappets, check the clearance after replacing the valves and adjust the shims.

Technical guide

The brand offered

Based in San Jose, California, SUPERTECH Performance has designed valves, springs and guides for racing for more than thirty years, and checks every batch by ultrasound, X-ray and laser.

How to choose

Both sets share the same head; the tappet type decides the length:

When reinforced valves become necessary

• Boost pressure raised
• Higher-lift camshafts or stiffer springs
• Raised rev limit
• Cylinder head rebuilt for drifting, track or rally
• Marked original valves or seats already reground

Compatible vehicles

OEM part number (inlet valve): 13201-58S11 (RB20DE) / 13201-59S11 (RB20DET)

Related products

With the head off, replace the exhaust valves of the RB20 as well: