Reinforced exhaust valves Honda Civic Type R K20C1

Honda engines covered

The K20C1 is Honda's 1,996 cc turbocharged four-cylinder (86 mm bore, 85.9 mm stroke) that has powered the Civic Type R since the 2015 FK2, then the FK8 from 2017 and the FL5 from 2022.

Its 16-valve cylinder head has 8 exhaust valves, two per cylinder, sitting in the gas flow that drives the turbine. The reinforced valves in this set have a 29.0 mm head, a 5.47 mm stem and a 114.7 mm overall length.

SUPERTECH reinforced exhaust valves

On a naturally aspirated engine, the head metal of an exhaust valve reaches 760 to 870 °C; turbocharged like the K20C1, it goes beyond 1,000 °C. About 75 % of that heat leaves through the seat and 20 % through the guide. A steel from the EV8 family drops from 550 MPa at 600 °C to 300 MPa at 800 °C: pushed further, the head overheats, fatigues, distorts and the seal on the seat deteriorates.

The HEVI-1060D-HS-8 is made from Inconel, a nickel-based superalloy that still holds 860 MPa at 732 °C and 554 MPa at 816 °C, about 85 % more than EV8 steel around 800 °C. Its stem is hollow and sodium filled: liquid from 97.8 °C, the sodium carries heat from the head to the stem, then to the guide. FERREA's F2394P and F2395P are made of Super Alloy, a nickel-based alloy from the Competition Plus range; the F6355, from the 6000 series, is made of EV8 stainless steel.

The HEVI-1060D-HS-8 stays at the K20C1 standard size: a 29.0 mm head, not enlarged, so the exhaust seats keep their diameter. The FERREA F2395P goes to 30.0 mm: the burnt gases leave faster, provided the exhaust seats are machined to that diameter.

Exhaust valve technical specifications

The HEVI-1060D-HS-8 is designed for the turbocharged K20C1, in standard size, in Inconel with a hollow sodium-filled stem.

Valve fitting

Before closing the cylinder head, compare the groove of the HEVI-1060D-HS-8 with the profile of the collets you are refitting.

With a standard size head, the 8 exhaust seats stay at the Honda machining diameter. With the FERREA F2395P, they must be machined to 30.0 mm.

Never drill or cut a sodium filled valve: in contact with water, sodium releases hydrogen and caustic soda.

Technical guide

Our brands

	SUPERTECH Performance, a Californian engine builder specialised in racing valvetrains for more than thirty years, offers the K20C1 an Inconel exhaust valve with a hollow sodium filled stem, in the engine's standard size.
	FERREA, founded in 1978 by Horacio Ferrea and Daniel Urrutia, makes its valves in Florida and Argentina. For the K20C1, it offers its Super Alloy valve from the Competition Plus range, in standard size and +1 mm, and its 6000 series in standard size.

How to choose

The choice comes down to head size and material:

When reinforced valves become necessary

• Higher boost pressure (sodium filled Inconel version)
• Remap with a larger turbo
• More aggressive camshafts or valve springs
• Repeated track days
• Cylinder head rebuild with marked exhaust valves

Vehicle compatibility

OEM part number (exhaust valve):

Don't forget the inlet valves

A K20C1 cylinder head off the engine is the right time to replace the inlet valves and the valve stem seals as well: