Reinforced inlet valves SUBARU EJ20 EJ205 EJ207 EJ255 EJ257

SUBARU engines covered

The EJ is Subaru's flat-four, with 16 valves and two camshafts on each cylinder head. This page covers its turbocharged versions: 2.0 litre (EJ20G, EJ20U, EJ20-GN, EJ205, EJ207, EJ20X, EJ20Y) from 170 to 320 hp and 2.5 litre (EJ255, EJ257, EJ25DET) from 211 to 400 hp. Since 1992 they have powered the Impreza WRX and WRX STi, the WRX, the turbocharged Forester and Legacy, the Outback and the Baja.

The engine has 8 inlet valves: Subaru lists them as 13201AA390, 13201AA391 then 13201AA371 on the EJ205, 13201AA510, 13201AA400 then 13201AA371 on the EJ207, and 13201AA400 then 13201AA371 on the EJ255. Their stem measures 5.955 to 5.970 mm for a length of 104.4 mm. Higher boost, sharper camshafts or more rpm load them far beyond standard use.

SUPERTECH and FERREA reinforced inlet valves

On every cycle the inlet valve opens to let in the air compressed by the turbo, drops back onto its seat and slides in its guide, dozens of times per second at high rpm. It works between 400 and 550 °C, and the chrome-silicon steel of an original valve falls from 500 MPa of strength at 500 °C to 250 MPa at 600 °C: it loses 50 % of its strength.

The SUPERTECH valves are black nitride stainless steel: nitriding hardens the surface and limits stem wear in the guide, and a back cut under the head clears the air flow. The FERREA Competition Plus valves, stainless with a chrome stem, gain 20 % in hot strength and fatigue resistance and make the seat last 25 % longer. The FERREA 6000 series valves are EV8 stainless steel: 650 MPa at 500 °C and 550 MPa at 600 °C, that is 30 % then 120 % better than the original steel.

Each brand offers the standard size (36 mm head) and the +1 mm size (37 mm); SUPERTECH adds a +0.5 mm size (36.5 mm). A wider head opens a larger flow area at the seat: the cylinder fills better and the engine gains power, provided the 8 inlet seats are cut to the new diameter.

Inlet valve technical specification

SIVN-1012-2-8: length and groove 0.5 mm lower than standard; SIVN-1014-2-8: 0.5 mm shorter than standard.

SIVN-1014-8: 4.3 mm stem tip, as standard. FERREA valves: 3.5 mm stem tip.

F1520P*8 and F1524P*8: Impreza WRX STi 2004 to 2008; F1524P*8 is fitted with FERREA K10074 collets.

F1967P*8 and F1965P*8: Impreza WRX EJ20 2001 to 2008, 19° Super Flo profile; F1965P*8 is fitted with FERREA K10061 collets.

F6077*8 and F6078*8: Impreza WRX EJ20 2001 to 2008 and WRX STi 2004 to 2008; F6078*8 is fitted with FERREA K10061 collets.

Fitting details

The +0.5 mm and +1 mm sizes need inlet seats cut to 36.5 mm or 37 mm; at standard size the seats keep their diameter.

The SUPERTECH valves are fitted with 6 mm, 6° single groove collets, two per valve.

After replacing the valves, check the inlet clearance, 0.18 to 0.22 mm cold, and reset it if needed.

Technical guide

Our brands

	SUPERTECH Performance has been making valves, springs and retainers for motorsport in San Jose, California, for more than thirty years. Every batch is checked by ultrasound, X-ray and laser, and part numbers are developed head by head with racing engine builders.
	FERREA Racing Components was set up in 1978 in Fort Lauderdale, Florida, by two engine builders from Argentina. Its valves are forged in one piece from bar stock and then fully machined on CNC equipment, and they run in NASCAR as well as in drag racing.

How to choose

The groove is the notch machined near the end of the stem, where the collets lock the retainer; here the choice comes down to size and length.

When reinforced valves become necessary

• Turbo pushed beyond its original boost
• Higher lift camshafts or stiffer springs
• Rev limiter raised
• Cylinder head rebuilt for rally, circuit or drift
• Worn original valves or seats already reground

Compatible vehicles

OEM part number (inlet valve): 13201AA390 / 13201AA391 / 13201AA371 / 13201AA400 / 13201AA510