Reinforced inlet valves SUBARU Legacy Outback EZ30 1998-2003

SUBARU engines covered

The EZ30 is Subaru's 3.0 litre 24-valve flat six. Its first generation powers the Legacy III (BE, BH) and the Outback (BH), from 1998 to 2003, with 209 or 220 hp depending on the version.

Its two cylinder heads carry 12 inlet valves in all. Track use, sharper camshafts or a higher rev limit load them more heavily than everyday driving.

SUPERTECH reinforced inlet valves

An inlet valve opens the way for fresh air, closes by striking its seat and slides constantly in its guide, at 400 to 550 °C. In this range, the chrome-silicon steel of ordinary valves drops from 500 MPa at 500 °C to 250 MPa at 600 °C: 50 % of its strength is gone.

SUPERTECH's SIVN-2304D-12 is made of black nitride stainless steel: its harder, smoother stem wears less in the guide. The head is dished, the stem is undercut below the head and the head is back cut to ease the airflow.

SUPERTECH supplies it as a +1 mm oversize with a 36 mm head: the opening grows and the cylinders fill better, once the inlet seats are cut to this diameter.

Inlet valve technical specification

Dished head.

Fitting details

The +1 mm size needs inlet seats cut to the diameter of the 36 mm head, work to plan with the cylinder head rebuild.

Technical guide

The brand offered

Based in California, SUPERTECH Performance has made valves, springs, retainers and guides for racing for more than thirty years, and checks each batch by ultrasound, X-ray and laser.

When reinforced valves become necessary

• Higher lift camshafts or stiffer springs
• Raised rev limit
• Supercharger or turbo fitted
• Cylinder heads rebuilt for track, hill climb or rally
• Worn original valves or seats already reground

Compatible vehicles

Related products

With the EZ30 cylinder heads off, also replace its 12 exhaust valves: