Reinforced exhaust valves Honda S2000 F20C F22C

Honda engines covered

The Honda S2000 roadster received two naturally aspirated 16-valve four-cylinder petrol engines: first the 1,997 cm³ F20C (87 mm bore, 84 mm stroke), built from 1999 to 2009 and known for revving very high, then from 2003 the 2,157 cm³ F22C, whose stroke is lengthened to 90.7 mm.

Its cylinder head carries 8 exhaust valves, Honda part number 14721-PCX-000: 31 mm head, 5.45 mm stem, held by original collets 14781-PR7-A01. Designed for a production engine that already spends long periods under heavy thermal load, they quickly reach their limits once tuning raises the load, the revs or the temperature of the exhaust gases.

SUPERTECH and FERREA reinforced exhaust valves

The exhaust valve is the path for the burnt gases. On a naturally aspirated engine its head reaches 760 to 870 °C; with forced induction it goes beyond 1,000 °C. Around 75 % of this heat leaves through the seat and about 20 % through the guide. Yet steel loses strength as it heats up: an EV8-family steel, used here as a reference, still holds 550 MPa at 600 °C but drops to 300 MPa at 800 °C. As soon as load, revs or boost pressure rise, the valve runs hotter, fatigues, can distort and ends up leaking.

Reinforced valves use materials designed for these heat levels, in particular Inconel, a nickel-based superalloy that keeps 554 MPa around 815 °C and 860 MPa at 730 °C: around 800 °C it offers about 85 % more strength than the reference steel. For its Competition Plus range, FERREA claims 20 % more hot strength and a seat life extended by 25 %. These engines can take four finishes: black nitride stainless steel from SUPERTECH, whose harder and smoother surface cuts friction and wear, Inconel from SUPERTECH, the one to choose with a turbo or supercharger, the chromed stem of the FERREA Competition Plus and the EV8 stainless steel with hard chrome stem of the FERREA 6000 series.

Two oversize heads are also listed, 31.5 mm and 32 mm: only the head diameter changes. Burnt gases leave the chamber faster, leaving extra space for the incoming air and helping to raise output. This requires a cylinder head with seats recut to the new size.

Exhaust valve technical specifications

Valve fitting

As each manufacturer requires, the valve is fitted with its own collets: KPR-5.5-7A-ST for the single groove SUPERTECH valves, steel K10034 for the FERREA valves. Original collets must never hold a single groove valve.

With a 31.5 or 32 mm head, the 8 exhaust seats must be recut to that diameter: plan a visit to the machine shop during the rebuild.

All these valves keep the original 5.5 mm stem: the factory guides can stay in place, provided they are still within tolerance once checked.

Technical guide

Our brands

	SUPERTECH, a Silicon Valley company, has spent over thirty years creating competition valves, valve springs, guides and titanium retainers. Whether in stainless steel, titanium or Inconel, every valve is engineered for a given engine and validated with leading tuners from drag strips, rally stages and race tracks.
	FERREA Racing Components, founded in 1978 by Daniel Urrutia and Horacio Ferrea, makes its valves in its own workshops in Florida and Argentina, in stainless steel as well as nickel-based superalloy or titanium. Engine builders on every continent fit them, from NASCAR to drag racing.

How to choose

Sitting under the retainer, the collets lock into the stem groove and hold the valve. The SUPERTECH valves have only one, clamped by their collets: what remains to choose is head size and material, which change what you gain.

When reinforced valves become necessary

• Higher lift camshafts or firmer valve springs
• Raised rev limit
• Forced induction added with a turbo or supercharger (Inconel version recommended)
• Cylinder head fully rebuilt for rally, drift or track
• Original valves worn, marked or already at repair size

Vehicle compatibility

OEM part number (exhaust valve): 14721-PCX-000 (F20C)

Don't forget the inlet valves

A rebuilt cylinder head also calls for new inlet valves and valve stem seals, to be replaced along with the exhaust valves. Here is what we offer for these engines: