Reinforced inlet valves HONDA D16A9

HONDA engines covered

The D16A9 is Honda's 1.6 litre four-cylinder petrol engine with double overhead camshafts and 16 valves, rated at 130 to 132 hp. It powers the Civic IV and V 1.6 i-16 and 160i, the CRX II 1.6 i-16 and the Concerto 1.6, built between 1987 and 1996.

It uses 8 inlet valves, two per cylinder, Honda part number 14711-PG6-000: 30.0 mm head, 6.6 mm stem and 105.5 mm overall length, held by 14781-PE0-003 collets. Designed for factory output, they soon reach their limits once sharper camshafts, stiffer springs, higher revs or a turbo are fitted.

SUPERTECH reinforced inlet valves

At high rpm the inlet valve opens and closes dozens of times every second to let fresh air in. Each cycle drops its head back onto the seat, and the stem keeps sliding up and down its guide. Between 400 and 550 °C the standard chrome-silicon steel weakens: it holds 500 MPa at 500 °C but only 250 MPa at 600 °C, a 50 % loss. Lift, spring rate, rpm and boost pressure all add to these loads.

SUPERTECH makes this valve from a racing-grade chrome-nickel stainless steel related to EV8 (21-4N). This alloy keeps 650 MPa at 500 °C and 550 MPa at 600 °C, that is 30 % then 120 % better than the standard steel. Thanks to the black nitride treatment its surface becomes harder and slicker, which cuts friction and wear of the stem inside its guide.

The part offered is a +0.5 mm oversize: its head measures 30.5 mm instead of 30.0 mm, while stem and length follow the original format. The wider passage at the seat improves cylinder filling, provided the inlet seats of the head are recut to this size.

Inlet valve technical specification

HIVN-1005-8: stem thinned under the head and back-cut head.

Fitting details

The collets must match the groove design: for this valve, SUPERTECH pairs its 7 degree KPR-6.6-LS collets.

The +0.5 mm oversize requires inlet seats cut for a 30.5 mm head, a machine shop job to plan with the cylinder head rebuild.

The D16A9 sets its valve clearance with adjusting screws on the rocker arms: after replacing the valves, check the clearance and adjust it.

Technical guide

The brand offered

SUPERTECH works from San Jose in California and has spent over thirty years developing racing valvetrain parts. Each valve is drawn for one specific engine, checked one by one with ultrasound, X-ray and laser, then proven by engine builders, from circuit to drag strip.

How to choose

On this engine the choice comes down to a single part: head size and finish decide which cylinder head it suits and what it brings over the standard valve.

When reinforced valves become necessary

• Sharper camshafts or stiffer valve springs fitted
• Rev limit raised
• Switch to forced induction, turbo or supercharger
• Cylinder head rebuild for track, rally or drift
• Standard valves marked, tired or ground to repair size

Compatible vehicles

OEM part number (inlet valve): 14711-PG6-000

Don't forget the exhaust valves

A head rebuild is the moment to renew inlet valves, exhaust valves and stem seals at the same time. These exhaust valves suit this engine: