Reinforced valve spring kit Nissan 370Z VQ37VHR

€1,607.35 (tax incl.)

Kit of 24 reinforced valve springs for the Nissan VQ37VHR 3.7 V6 24V engine.

Brand: SUPERTECH
Engines: VQ37VHR (370Z, Skyline V36, Fuga, Infiniti G37, Q50, Q60, Q70)
Springs: single conical
Contents: springs, titanium upper retainers, collets

Nissan engine covered

These springs are made for the naturally aspirated 3.7 litre 24-valve V6 coded VQ37VHR. It sits under the bonnet of the Nissan 370Z (Z34), the Skyline V36 and the Fuga, and of a long list of Infiniti models: G37, EX37, FX37, M37, Q40, Q50, Q60, Q70, QX50 and QX70.

As standard, each valve is closed by a single spring: 13203-EY01A on the inlet side (01.2013 to 02.2015), 13203-JK21A then 13203-JK22A on the exhaust side. They come with upper retainers 13209-AC700 (until 01.2013) then 13209-1KC0A, lower spring seats 13205-53Y00 and collets 13210-53Y00.

SUPERTECH reinforced valve spring kit

Once the lobe is past its peak, the spring pushes the valve back onto its seat. As revs rise, inertia wins out: the valve lifts off, bounces and may hit the piston. Engine builders call it valve float.

This kit supplies single conical springs, 12 inlet and 12 exhaust: 311 N and 267 N on the seat, then 876 N and 827 N at 10 mm lift.

Valve spring kit technical specification

Part number	Brand	Springs	Outer / inner Ø	Seat pressure	Open pressure	Rate	Max lift	Kit contents
SPRK-N370Z-1	SUPERTECH	Single conical	Inlet: base 28.0 / 18.8 mm, top 24.2 / 14.5 mm Exh.: base 27.7 / 19.7 mm, top 23.2 / 15.2 mm	Inlet: 311 N at 39.4 mm Exh.: 267 N at 36.5 mm	Inlet: 876 N at 10 mm Exh.: 827 N at 10 mm	56.5 N/mm	Inlet: 14.0 mm Exh.: 13.5 mm	24 springs (12 inlet, 12 exhaust), 24 titanium upper retainers, collets; original lower spring seats kept

Valve spring kit fitting details

Part	Nissan original	Reinforced spring kit
Spring	Inlet 13203-EY01A; exh. 13203-JK21A, 13203-JK22A	Kit specific
Retainer	13209-AC700, 13209-1KC0A	Kit specific (titanium)
Spring seat	13205-53Y00	Original kept
Collets	13210-53Y00	Supplied with the kit

The SUPERTECH SPRK-N370Z-1 kit contains 24 single conical springs, 12 for the inlet side and 12 for the exhaust side, 24 titanium upper retainers and the collets. The original lower spring seats stay in place.

Installed height is the gap, valve closed, between the lower spring seat carrying the spring and the upper retainer. Each load listed holds at its own height: 39.4 mm at the inlet, 36.5 mm at the exhaust. A taller height, say after the seats are recut in the head, subtracts the spring rate from the load for every millimetre gained (see table).

	SUPERTECH
Installed height	Inlet: 39.4 mm Exh.: 36.5 mm
Seat pressure at this height	Inlet: 311 N Exh.: 267 N

Technical guide

Our brands

SUPERTECH, based in California, has supplied racing engine builders for more than thirty years. Its springs are cut from steel wire alloyed with chromium, silicon and vanadium, its upper retainers are made of titanium, and each batch goes through ultrasound, X-ray and laser inspection.

How to choose

A stiffer spring lets the engine run higher in the rev range, take a livelier camshaft or add boost without the valves bouncing. At the seat this kit delivers 311 N on the inlet side and 267 N on the exhaust side, as the table above sums up. Before buying, measure the real lift of your camshaft: it must stay below 14.0 mm on the inlet side and below 13.5 mm on the exhaust side, the limits of these springs. The check takes a few minutes and avoids a wrong purchase.

Criterion	Key point
Choosing the pressure	Three things guide the choice: camshaft lift, the revs you are aiming for and any boost pressure. When one of them goes up, the load has to follow, without passing the maximum lift of the springs. This kit gives 311 N on the seat at the inlet and 267 N at the exhaust. Aiming higher than needed brings nothing: cams and tappets wear faster.
Single or double spring	Each valve gets a single spring whose coil narrows towards the top: that is the conical shape. No inner spring is added, unlike double spring kits. The titanium upper retainers and the collets come in the kit, and the original lower spring seats are kept.

When reinforced springs become necessary

Camshaft with a higher lift than standard
Rev limiter raised well above standard
Supercharger or turbo added, or more boost
Head reworked for circuit, drift or rally
Worn springs, or valve float at high revs

Compatible vehicles

Model	Engine code	Years
Infiniti EX37 (EX 37 / 37 AWD)	VQ37VHR	from 2008
Infiniti FX37 (FX 37 / 37 AWD)	VQ37VHR	from 2008
Infiniti G37 (G 37 / 37 IPL / 37 X)	VQ37VHR	from 2007
Infiniti M37 (Y51)	VQ37VHR	from 2010
Infiniti Q40 3.7 / 3.7 AWD	VQ37VHR	from 2014
Infiniti Q50 3.7 V6 VVEL	VQ37VHR	from 2013
Infiniti Q60 3.7 / 3.7 AWD / 3.7 IPL	VQ37VHR	from 2013
Infiniti Q70 (Y51) 3.7 / 3.7 AWD	VQ37VHR	from 2013
Infiniti QX50 I 3.7 V6 VVEL	VQ37VHR	from 2013
Infiniti QX70 3.7 AWD / 37 RWD	VQ37VHR	from 2013
Nissan 370Z (Z34) 3.7 / NISMO	VQ37VHR	from 2009
Nissan Fuga II (Y51) 370 GT / 370 GT 4WD	VQ37VHR	from 2009
Nissan Skyline (V36) 370GT / 370GT 4x4	VQ37VHR	2007-2015
Nissan Skyline Crossover (J50) 370GT / 370GT FOUR	VQ37VHR	from 2009

OEM part number (valve spring): exhaust 13203-JK21A then 13203-JK22A; inlet 13203-EY01A

Important: this kit is for the Nissan VQ37VHR engine (3.7 V6 24V). The 3.5 V6 engines of the VQ family, such as the VQ35HR, are not covered. Check your engine code before ordering.