Reinforced inlet valves HONDA H23A2 H23A3

HONDA engines covered

The H23A2 and H23A3 are Honda's 2,259 cc double overhead camshaft 16-valve four-cylinders, from 158 to 160 hp. They power the Prelude IV 2.3 i 16V and the Accord V 2.3 i SR, from 1992 to 1996.

Each engine has 8 inlet valves, two per cylinder: the 14711-PT2-000 original valve has a 34.0 mm head and a 6.6 mm stem. A sharper camshaft, stiffer springs, a higher rev limit or forced induction ask far more of them than stock use.

SUPERTECH 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.

SUPERTECH supplies this valve in +1 mm oversize: 35.0 mm head, 6.58 mm stem, 103.5 mm length. The wider head lets more air through and improves filling, provided the inlet seats are cut to 35.0 mm.

Inlet valve technical specification

Fitting details

The +1 mm size needs inlet seats cut to 35.0 mm, workshop work to plan with the cylinder head rebuild.

Technical guide

The brand offered

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.

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

OEM part number (inlet valve): 14711-PT2-000