Reinforced inlet valves NISSAN 370Z VQ37VHR

NISSAN engines covered

The VQ37VHR is Nissan's 3.7 litre 24-valve V6 with four overhead camshafts and VVEL variable lift on the inlet side, from 328 to 355 hp depending on version. It powers the 370Z Z34 coupé and roadster since 2009, as well as the Skyline V36 370GT, Skyline Crossover 370GT and Fuga II 370 GT.

The engine has 12 inlet valves, held by 13210-53Y00 collets under 13209-AC700 retainers, then 13209-1KC0A from 2013. A supercharger, sharper camshafts or a higher rev limit load them well beyond stock use.

SUPERTECH reinforced inlet valves

Each inlet valve of the V6 opens dozens of times per second at high revs, then strikes its seat and slides in its guide. It runs between 400 and 550 °C, where the original chrome-silicon steel falls from 500 MPa at 500 °C to 250 MPa at 600 °C: 50 % of its strength is gone.

SUPERTECH makes these valves from a racing stainless steel of the EV8 family, which keeps 650 MPa at 500 °C and 550 MPa at 600 °C, 30 % and then 120 % more than the original steel. Black nitriding makes the stem harder and smoother, so it wears less in the guide.

SUPERTECH supplies it in +1 mm oversize: 37.7 mm head, 5.97 mm stem and 100.2 mm length. The wider head opens a larger passage at the seat: the cylinder fills better and the engine gains power, with the inlet seats cut to the new size.

Inlet valve technical specification

SUPERTECH: dished head, undercut stem under the head and back cut.

Fitting details

The +1 mm size requires the inlet seats to be cut to 37.7 mm, workshop work to plan with the cylinder head rebuild.

Technical guide

The brand offered

SUPERTECH works out of San Jose, California, and has supplied valvetrain parts for racing engines for more than 30 years: valves, springs, retainers and guides. Each part number starts from a specific cylinder head, goes through ultrasound, X-ray and laser checks, then is proven with engine builders, from drag strip to circuit.

When reinforced valves become necessary

• Higher-lift camshafts or stiffer springs
• Raised rev limit
• Turbo or supercharger fitted
• Cylinder head rebuilt for circuit, hill climb or rally
• Original valves marked, worn or already reground

Compatible vehicles

Related products

For a rebuilt VQ37VHR cylinder head, the reinforced exhaust valves are available here: