Reinforced exhaust valves Mitsubishi Eclipse 2.0 420A

Mitsubishi engines covered

The second generation Mitsubishi Eclipse (D3_A) uses, in 2.0 RS form from 1995 to 1999, the 420A, a 16-valve 2.0.

This engine has 8 exhaust valves. The set offered is in standard size, with a 30.7 mm head, a 5.95 mm stem and a 110 mm overall length.

SUPERTECH reinforced exhaust valves

The exhaust valve is the part that drives burnt gases out of the cylinder, right after ignition. In an unboosted engine like the 420A, its head metal ranges between 760 and 870 °C, and would climb above 1,000 °C if a turbo or supercharger were grafted on. To cool down, it relies on the seat, which absorbs around 75 % of the heat, and on the guide, which takes nearly 20 %. Steel dislikes these levels: an EV8 grade goes from 550 MPa near 600 °C to 300 MPa near 800 °C. With more rpm, lift or load, the head runs too hot, fatigues, distorts and the seal at the seat disappears, which costs compression and power on every stroke.

SUPERTECH makes the MEVN-1420-8 in stainless steel, chosen to keep its strength in exhaust heat, and dresses its stem in a chrome coating. This hard, smooth layer limits friction and wear of the stem in its guide, where a tired original valve eventually develops play and centres badly on its seat. Designed for the heat of an engine without forced induction, this valve is aimed first at a tuned, unboosted 420A used on the road, for track days or in hill climbs, rather than at an engine converted to turbo.

The head keeps its original 30.7 mm diameter, so the valve sits on the factory seats. A recut is enough to restore a continuous contact, which ensures the head cools well against the cylinder head.

Exhaust valve technical specifications

Valve fitting

Before reassembly, check that the collets suit the lock groove of the MEVN-1420-8.

In standard size, the MEVN-1420-8 fits exhaust seats cut at 30.7 mm.

Clearance between the 5.95 mm stem and the guides is checked during the cylinder head rebuild.

Technical guide

Our brand

SUPERTECH, born in the heart of Silicon Valley, has equipped racing teams for over three decades with valves, guides, springs and titanium retainers. Each stainless, titanium or Inconel valve is created for one engine, then proven by tuners on rally stages, circuits and drag strips.

How to choose

The 420A takes only one exhaust valve: the decision rests on the condition of the seats, to be checked before fitting, and on the use planned for the Eclipse, which guides the choice of the parts fitted around it.

When reinforced valves become necessary

• More aggressive camshafts or stiffer valve springs
• Rev limit pushed back by a new map
• Track days, hill climbs or slaloms
• Cylinder head rebuild with tired exhaust valves
• Original valves pitted, burnt or no longer closing properly

Vehicle compatibility

OEM part number (exhaust valve):

Don't forget the inlet valves

With the 420A cylinder head on the bench, renew the inlet valves too, along with every valve stem seal for a fully renewed top end. The seals for the Eclipse: