Reinforced inlet valves SUPERTECH FORD HYDA JZDA

FORD engines covered

The 2.5 litre turbocharged inline five-cylinder 20-valve engine, designed by Volvo, powers the Ford Focus II ST (engine code HYDA, 225 hp) and the Focus II RS (code JZDA, 305 hp, 350 hp on the RS 500). In Australia, it is fitted to the Focus XR5 Turbo and RS.

This engine has 10 inlet valves, two per cylinder. A remap, a bigger turbo, sharper camshafts or higher revs subject them to more heat, harder impacts on the seat and more friction in the guide than they were designed for.

SUPERTECH reinforced inlet valves

In the 2.5 litre turbocharged five-cylinder of the Focus ST and RS, the inlet valve never gets a break: as the rev counter needle climbs, it moves aside and snaps back at a high rate, dozens of strokes each second, feeding the cylinder with the charge the turbo has packed in; its head taps its seat on every closing, and its stem keeps travelling inside the guide. Thermally it operates between 400 and 550 °C, where the usual chrome-silicon grade begins to yield: 500 MPa at 500 °C, then 250 MPa from 600 °C, just beyond, a 50 % loss of strength. Let the cam lift further, the springs stiffen, the engine rev or blow harder, and the pounding, rubbing and heating all get far tougher.

SUPERTECH forges these valves from EV8 (21-4N), a chrome-nickel stainless designed for racing. This metal keeps 650 MPa at 500 °C, 30 % above chrome-silicon steel, and 550 MPa at 600 °C, 120 % above, at a point where the original part has already lost half its capacity. Black nitriding finishes every valve: the surface comes out harder and slicker, so stem and guide wear markedly more slowly, even at sustained high rpm.

Two sizes are offered. The standard size keeps the 31 mm head; the +1 mm oversize takes it to 32 mm while stem and length stay put. That millimetre widens the seat opening, every cylinder breathes in more and the five-cylinder gains horsepower, provided the head's seats are recut to the larger diameter.

Inlet valve technical specifications

Valve fitting

These valves have 3 grooves with an MK6H profile and are fitted with collets of this profile.

The +1 mm oversize requires cylinder head seats cut to the diameter of the new head, a job to plan with the cylinder head rebuild.

Technical guide

The brand offered

SUPERTECH, a maker established in San Jose (California), has put its skills to work on racing valvetrains for more than 30 years. Each model is drawn up around one engine, run through ultrasonic probing, radiographic examination and laser readings, before confirmation by tuners.

How to choose

Both references share the same 3 grooves and stem; only size separates them, meaning head diameter, chosen according to the condition of the seats.

When reinforced valves become necessary

• Remap with markedly raised boost pressure
• Bigger turbocharger or more aggressive cam profiles
• Cut-off rpm pushed back
• Head redone for a track, rally or drift five-cylinder
• Stock valves damaged, fatigued or reground once before

Vehicle compatibility

Related products

On a rebuilt 2.5 litre five-cylinder head, the exhaust side needs the same attention as the inlet: the reinforced exhaust valves are offered here: