Reinforced exhaust valves Honda D16Y D16Z6 D17A R18A

Honda engines covered

The single camshaft, 16 valve Honda four-cylinders on this page span three Civic generations and the CRX III: 1.6 litre D16Z6 and D16Y (107 to 129 hp), 1.7 litre D17A (125 to 131 hp) in the Civic VII, then the 1.8 litre R18A (140 and 141 hp) in the Civic VIII and IX.

Each has 8 exhaust valves. On the D17A5, the original part 14721-P08-000 measures 26.0 mm across the head, 5.5 mm at the stem and 116.0 mm long, dimensions matched by the SUPERTECH standard valve. With a sharper camshaft or a turbo, this is the valve that takes the extra heat.

SUPERTECH reinforced exhaust valves

Naturally aspirated, the head metal of an exhaust valve works between 760 and 870 °C; it goes past 1,000 °C once a turbo or supercharger is fitted. The head cools by contact, about 75 % through the seat and 20 % through the guide. The original steel, measured against the EV8 family, holds 550 MPa at 600 °C and 300 MPa at 800 °C; beyond that the head fatigues, distorts and no longer closes its seat.

The HEVN-1012 and HEVN-1002 are black nitrided stainless steel, with a 5.45 mm stem and a 1.9 mm tip. The HEVI-1102 is Inconel, a nickel superalloy that keeps 860 MPa at 732 °C and 554 MPa at 816 °C, about 85 % more than EV8 steel around 800 °C: this is the version to choose for forced induction. For the D16Z6 and D16Y, FERREA offers its Super Alloy valve from the Competition Plus range (F1821P, F1495P), its flat head 5000 series (F5512, F5514) and its 6000 series (F6067, F6070).

The HEVN-1002 widens the head to 26.5 mm (+0.5 mm) and the HEVI-1102 to 27.0 mm (+1 mm): burnt gases leave more easily, the cylinder fills better and power rises; the exhaust seats are then machined to the new diameter. The F1495P, F5514 and F6070 also go to 27.0 mm.

Exhaust valve technical specifications

Valve fitting

Compare the groove of the chosen valve with that of the original 14781-PJ7-003 collets before reassembly.

The HEVN-1012 fits the original seats; the HEVN-1002 and HEVI-1102 need all 8 seats recut to size.

Honda fits 12210-PZ1-003 and 12211-PZ1-003 valve stem seals as original (D17A5, D16Y5, R18A1), and 12210-P45-G01 / 12211-P45-G01 on the R18A2.

Technical guide

Our brands

	SUPERTECH Performance has been producing racing valves and valvetrain parts in California for more than thirty years. For these Honda engines it supplies nitrided stainless steel in standard size and +0.5 mm, and Inconel in +1 mm.
	FERREA, founded in 1978 by Horacio Ferrea and Daniel Urrutia, makes its valves in Florida and Argentina. For the D16Z6 and D16Y, it offers three ranges, Competition Plus, 5000 series and 6000 series, in standard size or +1 mm.

How to choose

The size sets the seat work, the material sets the heat resistance:

When reinforced valves become necessary

• Turbo or supercharger added (Inconel version recommended)
• Sharper camshaft or valve springs changed
• Regular track days
• Cylinder head rebuild with worn exhaust valves
• Enlarged seats to gain flow

Vehicle compatibility

OEM part number (exhaust valve): 14721-P08-000 (D17A5)

Don't forget the inlet valves

For a cylinder head rebuilt in one go, also think of the inlet valves: