Reinforced inlet valves HONDA D16A6

HONDA engines covered

The D16A6 is Honda's 1,590 cc single overhead camshaft 16-valve four-cylinder, without VTEC, from 109 to 110 hp. It powers the Civic IV 1.6 i 16V, in front-wheel drive, 4x4 and Shuttle 4WD form, and the CRX II 1.6 Si, from 1987 to 1991.

It has 8 inlet valves, two per cylinder, with a 5.48 mm stem. A sharper camshaft, stiffer springs, a higher rev limit or forced induction ask far more of them than stock use.

SUPERTECH and FERREA reinforced inlet valves

On the inlet side, each valve opens and closes dozens of times a second at high rpm, strikes its seat and slides constantly in its guide, at 400 to 550 °C. At these temperatures the chrome-silicon steel of stock valves drops from 500 MPa at 500 °C to 250 MPa at 600 °C: it loses 50 % of its strength.

SUPERTECH makes these valves from an EV8-type racing stainless steel: 650 MPa at 500 °C and 550 MPa at 600 °C, i.e. 30 % then 120 % more than stock steel. Their black nitride treatment hardens and smooths the surface, which cuts friction and stem wear in the guide. The FERREA valves belong to the Competition Plus series: the maker credits them with 20 % more hot strength and fatigue resistance, and a seat life 25 % longer.

SUPERTECH supplies it in the engine's standard size: 29.0 mm head, 5.48 mm stem, 115.0 mm length. FERREA offers it at 29.0 mm and as a +1 mm oversize, 30.0 mm head, 5.5 mm stem: the wider head opens the passage at the seat and improves filling, with the inlet seats cut to this size.

Inlet valve technical specification

Fitting details

Valve clearance is adjustable on this engine: after replacing the valves, check and set it (0.17 to 0.22 mm cold on the inlet side).

Technical guide

Our brands

	SUPERTECH, based in San Jose, California, has designed valvetrain parts for racing engines for more than 30 years: valves, springs, retainers, guides. Each valve is drawn for a given cylinder head, checked by ultrasound, X-ray and laser, then proven with engine builders, at the drag strip as on the circuit.
	FERREA Racing Components has operated in Fort Lauderdale, Florida, since two Argentine engine builders founded it in 1978. The company forges each valve in one piece from steel bar, then machines it end to end on CNC; its parts are found in NASCAR as well as drag racing.

When reinforced valves become necessary

• Higher-lift camshafts or stiffer springs
• Raised rev limit
• Turbo or supercharger fitted
• Cylinder head rebuilt for circuit, hill climb or rally
• Original valves marked, worn or already reground

Compatible vehicles

Related products

For a rebuilt D16A6 cylinder head, the reinforced exhaust valves are on this page: