Reinforced exhaust valves Nissan 300ZX Z31 VG30T

Nissan engines covered

The VG30T is the 3.0 litre turbocharged V6 with one camshaft per bank and 12 valves that Nissan fitted in the mid-1980s, notably in the 300ZX and Fairlady Z of the Z31 series.

With one exhaust valve per cylinder it has 6 of them, with a 35.1 mm head in the version offered, an 8 mm stem and a 124.5 mm overall length. Sitting just upstream of the turbo, they take both the pressure and the heat of the gases.

FERREA reinforced exhaust valves

On the VG30T, the six exhaust valves open just upstream of the turbo and see gases that are both very hot and under pressure. With boost, their head metal passes 1,000 °C, whereas an unboosted engine stays at 760 to 870 °C. Roughly three quarters of that heat flows out through the seat and about a fifth through the guide, provided every closing is clean and the valve sits squarely on its seat. Steel, taken as a reference with the EV8 family, keeps only 300 MPa near 800 °C after 550 MPa near 600 °C. The higher the boost, the more the head suffers: it fatigues, buckles and then lets gases escape at the seat.

FERREA makes both valves offered for this V6 in Super Alloy, a nickel alloy designed to hold firm where steel softens, which makes it the natural material for a turbo engine. Under raised boost, with a more aggressive map or during repeated track sessions, the head keeps its geometry and goes on closing properly, cycle after cycle. Both references retain the 8 mm stem and 124.5 mm length of the production valve; only the head differs, leaving a choice between a like-for-like rebuild and a lightly reworked cylinder head.

In +1 mm oversize, the head grows from 35.1 to 36.1 mm. Burnt gases escape more quickly, which improves filling with fresh charge on the next cycle and serves power; the 6 seats are machined to this new diameter.

Exhaust valve technical specifications

Valve fitting

Compare the lock groove with the collets you reuse before refitting the springs.

At 35.1 mm the seats are left as they are; with the F1846P, the 6 exhaust seats are cut to 36.1 mm.

Both part numbers keep an 8 mm stem and a 124.5 mm overall length: the original guides are fine if they are within tolerance.

Technical guide

Our brand

FERREA Racing Components was created in 1978 by two enthusiasts, Horacio Ferrea along with Daniel Urrutia. Its plants in Florida and Argentina turn out valves made of stainless steel, of titanium or of nickel-based superalloy, chosen by tuners and engine shops on every continent.

How to choose

Both FERREA valves listed for the VG30T share material and stem dimensions: the choice therefore comes down to head size, set by the condition of the six seats and by the level of tuning planned for the engine.

When reinforced valves become necessary

• Raised boost or a larger turbocharger fitted
• Sharper cam profiles, uprated valve springs
• Engine map reworked for more power
• Repeated track days or hill climb events
• Production valves burnt, pitted or leaking compression at the seat

Vehicle compatibility

OEM part number (exhaust valve): 13202-V6510, 13202-07P00

Don't forget the inlet valves

Once the VG30T cylinder heads are stripped, take the chance to fit new inlet valves as well as twelve valve stem seals: the valve train will be fully renewed: