Reinforced exhaust valves Nissan 370Z VQ37VHR

Nissan engines covered

The VQ37VHR is Nissan's 3.7 litre 24-valve V6 with VVEL variable valve lift, powering the 370Z Z34 since 2009 as well as the Skyline 370GT, Skyline Crossover and Fuga 370 GT.

Its two cylinder heads hold 12 exhaust valves, two per cylinder. SUPERTECH offers them with a 5.96 mm stem and a 94.7 mm overall length.

SUPERTECH reinforced exhaust valves

The head of an exhaust valve sits in the burnt gases: its metal reaches 760 to 870 °C naturally aspirated and passes 1,000 °C with forced induction. Heat leaves mainly through the seat, about 75 %, then through the guide, about 20 %. An EV8 family steel holds only 300 MPa at 800 °C against 550 MPa at 600 °C: overheated, the head fatigues, distorts and the seal deteriorates.

The NEVI-1038F-12 is made of Inconel, a nickel-based superalloy that keeps 860 MPa at 732 °C and 554 MPa at 816 °C, about 85 % more than EV8 steel around 800 °C; its head is flat.

SUPERTECH sells it at +1 mm, a 31.4 mm head: the gas passage widens, provided the 12 exhaust seats are machined to that diameter.

Exhaust valve technical specifications

SUPERTECH note: the NEVI-1038F is listed as "31.4 (+1)", "Flat" and "Oversize" for the 370Z / VQ37VHR.

Valve fitting

On reassembly, check that the chosen collets match the groove of the NEVI-1038F-12.

With a 31.4 mm head, the 12 exhaust seats are machined to the new size before fitting.

Each cylinder head takes 6 valves from the same set, with identical 5.96 mm stem and 94.7 mm length.

Technical guide

Our brand

SUPERTECH Performance, a Californian maker of racing valves and valvetrains for more than thirty years, offers the VQ37VHR a flat head Inconel exhaust valve at +1 mm.

How to choose

A single part number is offered for this engine:

When reinforced valves become necessary

• Supercharger or turbo fitted (Inconel version recommended)
• More aggressive camshafts or firmer springs
• Repeated track days
• Rebuild of both cylinder heads with worn exhaust valves
• Enlarged seats to gain flow

Vehicle compatibility

OEM part number (exhaust valve):

Don't forget the inlet valves

With the VQ37VHR cylinder heads off, also think of the inlet valves and the valve stem seals.