Reinforced exhaust valves Nissan Skyline R34 RB20DE RB25DE RB25DET NEO

Nissan engines covered

The RB « NEO » engines are the 24-valve straight sixes of the R34 Skyline, from 1998 to 2002: the 2 litre RB20DE NEO, the 2.5 litre RB25DE NEO and the turbocharged RB25DET NEO, in saloon and coupé form.

Each has 12 exhaust valves, two per cylinder: original part number 13202-5L315 on the RB20DE NEO, 13202-5L715 on the RB25DE NEO and RB25DET NEO. FERREA reproduces them with a 5.96 mm stem and a 97.95 mm overall length.

FERREA reinforced exhaust valves

The metal of an exhaust valve head sits between 760 and 870 °C naturally aspirated and passes 1,000 °C on a boosted engine. The seat removes nearly 75 % of it, the guide about 20 %. An EV8 family steel keeps 550 MPa at 600 °C but only 300 MPa at 800 °C: the head fatigues, distorts and the seat seal is lost.

Both part numbers belong to FERREA's Competition Plus range, stated with 20 % more hot strength and 25 % longer seat life: a useful margin on an RB25DET NEO running raised boost.

The F1936P enlarges the head by 1 mm, from 29.65 to 30.65 mm: burnt gases leave faster and the cylinder empties better, provided the 12 exhaust seats are machined to that diameter.

Exhaust valve technical specifications

F1935P: 29.65 mm head, standard size; F1936P: 30.65 mm head, +1 mm; 5.96 mm stem, 97.95 mm overall length.

Valve fitting

On reassembly, check that the collets engage properly in the groove of the FERREA valves.

The F1935P fits on seats reground at standard size; the F1936P needs seats machined to 30.65 mm.

Replace the 12 exhaust valve stem seals at the same time and fit valves from the same set.

Technical guide

Our brand

FERREA, founded in 1978, makes its valves in Florida and Argentina. For the RB NEO engines of the R34 Skyline it offers its Competition Plus range at standard size and +1 mm.

How to choose

The choice is about head size:

When reinforced valves become necessary

• Raised boost on an RB25DET NEO
• Camshafts with higher valve lift
• Track, drift or drag racing
• Cylinder head rebuild with burnt exhaust valves

Vehicle compatibility

OEM part number (exhaust valve): 13202-5L315 (RB20DE NEO), 13202-5L715 (RB25DE NEO, RB25DET NEO)

Don't forget the inlet valves

With the RB NEO cylinder head off, replace the inlet valves and the valve stem seals too.