Exhaust valve guides Subaru EJ20 EJ25 turbo

Applicable Subaru engines

This set fits the exhaust side of the 2.0 and 2.5 litre Subaru turbo flat-fours: EJ205, EJ207, EJ20G, EJ20U, EJ20X, EJ20Y, EJ255, EJ257 and EJ25DET. It covers the Impreza, WRX, Forester, Legacy, Outback and Baja.

The 8 exhaust valves of the head each turn in a guide pressed into the aluminium. Subaru lists this guide as 13213-AA120: 47.5 mm long, 11.1 mm outside diameter and a 6 mm valve stem.

FERREA and SUPERTECH exhaust valve guides

At the exhaust port the stem takes the heat of the burnt gas. The guide keeps it centred on its seat, passes some of that heat to the cylinder head while retaining the seal. Once worn, the valve tilts, closes badly and lets oil reach the port: blue smoke, higher oil use and weaker compression.

According to the FERREA catalogue, this copper-based bronze, made from American raw material, gets an in-house heat treatment meant to carry heat away better, hold up at temperature, wear more slowly and lubricate the stem. Precise CNC machining takes titanium and stainless alike. SUPERTECH prefers a manganese bronze that, the brand indicates, sheds heat far more efficiently than the sintered guides of the standard engine. The set gathers the 8 exhaust guides of one head, normally matched with reinforced valves: half of the engine's guides, the other half being on the inlet side.

Valve guide technical specifications

Valve guide installation

Technical guide

Our brands

	FERREA dates from 1978 and Fort Lauderdale, Florida. Its two plants, American and Argentine, build guides, valves, springs and stem seals for racing and high-performance engines.
	Based in Silicon Valley for three decades and more, SUPERTECH designs competition valve train parts, calculated by finite elements and then tried with engine builders.

Standard or oversize?

FERREA guides come in standard size or in a 0.025 mm (0.001") oversize. SUPERTECH ships the oversize only, 11.08 mm outside diameter.

Manganese bronze

An alloy dominated by copper, into which manganese, aluminium, iron and a touch of zinc are blended. Hard and resistant to repeated rubbing and corrosion, it is used for highly stressed bushes, hence its place in a guide, against which the stem rubs on every cycle.

When valve guides must be replaced

• Oil use through the exhaust valve stems
• Reinforced valves meant for a worn cylinder head
• Racing engine whose head must be rebuilt
• Whole valve train due for renewal

Vehicle compatibility

OEM reference (exhaust valve guide): 13213-AA120

Important: FERREA lists these guides for the EJ20 engines of the Impreza WRX and STI 2001-2008. For the EJ25 turbo, only SUPERTECH guides are offered.

Remember the inlet guides and valve stem seals

Fresh guides need fresh stem seals: FERREA VS1015 on the exhaust side, per its catalogue.