Reinforced exhaust valves Subaru EJ20 EJ205 EJ207 EJ255 EJ257

Subaru engines covered

16-valve flat-four engines, most of them turbocharged, the EJ units on this page come as 2 litre (EJ20-GN, EJ20G, EJ20U, EJ205, EJ207, EJ20X, EJ20Y) and 2.5 litre (EJ255, EJ257, EJ25DET). From 1992 to 2022 they power the Impreza GT, WRX and STi, the turbocharged Forester, the Legacy and Outback, then the WRX and WRX STi.

Each has 8 exhaust valves: 13202AA400 and 13202AA401 on the EJ205, 104.7 mm long with a 5.945 to 5.960 mm stem, 13202AA520, 13202AA410 and 13202AA411 on the EJ207, 13202AA530, 13202AA570, 13202AA630 and 13202AA660 on the 2.5 litre. Built for standard power, they suffer once tuning raises boost, revs or gas temperature.

FERREA and SUPERTECH reinforced exhaust valves

The burnt gases leave through the exhaust valve, and it is the part that runs hottest: the metal of its head reaches 760 to 870 °C on a naturally aspirated engine and goes beyond 1,000 °C when turbocharged, as most of these EJ engines are. Around 75 % of that heat flows through the seat and 20 % through the guide. An EV8 family valve steel still withstands 550 MPa at 600 °C but only 300 MPa at 800 °C: beyond that, the head overheats, fatigues, may distort and no longer seals.

The reinforced versions use materials made for these temperatures. SUPERTECH offers black nitrided stainless steel, whose hardened, smooth surface limits friction and wear, Inconel, a nickel-based superalloy holding 860 MPa at 730 °C and still 554 MPa near 815 °C, about 85 % more than EV8 steel near 800 °C and recommended with a turbo, and a hollow sodium filled Nimonic version that carries heat from the head to the stem. FERREA supplies its 6000 series special alloy and the nickel-based Super Alloy of its Competition Plus range, with 20 % more hot strength and 25 % longer seat life.

Larger heads are also offered: 32.5 mm (+0.5 mm) and 33 mm (+1 mm) instead of 32 mm. The burnt gases leave the cylinder faster, to the benefit of the fresh charge and of power. They fit a cylinder head with seats machined to that size.

Exhaust valve technical specifications

Valve fitting

On reassembly, each valve gets sound collets, original (13210AA020) or K10061, seated properly in the stem groove; a marked collet is replaced.

A 32.5 or 33 mm head needs exhaust seats machined to its diameter: the cylinder head then goes to the machine shop during its rebuild.

The SEVN-1012-2-8 and SEVI-1014-2-8 are 0.5 mm shorter (104.2 mm), with the groove moved by the same amount: check the stem height on reassembly.

Technical guide

Our brands

	SUPERTECH Performance, based in Silicon Valley, has designed valves, springs, titanium retainers and guides for racing for more than thirty years. Each valve, in stainless steel, titanium or Inconel, is developed for a specific engine and proven with drag racing, rally and circuit engine builders.
	FERREA Racing Components, launched in 1978 by Horacio Ferrea and Daniel Urrutia, machines its valves in Florida and Argentina, from stainless steel to titanium by way of nickel-based superalloys. Engine builders all over the world, from NASCAR to drag racing, fit its parts.

How to choose

All these valves keep the engine's 5.96 mm stem: what remains to choose is the head size and the material, according to the tuning and the condition of the cylinder head.

When reinforced valves become necessary

• Sharper camshafts or stiffer valve springs
• Higher rev limit
• Raised boost pressure or a bigger turbo (Inconel version recommended)
• Cylinder head rebuild on a rally, circuit or drift car
• Production valves marked, worn or already at repair size

Vehicle compatibility

OEM part number (exhaust valve): 13202AA400, 13202AA401, 13202AA410, 13202AA411, 13202AA520 (EJ205, EJ207, EJ20X) ; 13202AA530, 13202AA570, 13202AA630, 13202AA660 (EJ255, EJ257)

Don't forget the inlet valves

With an EJ cylinder head off, take the opportunity to replace the inlet valves and valve stem seals too, and rebuild with an entirely new valvetrain.