Reinforced inlet valves MITSUBISHI 3000 GT 6G72

MITSUBISHI engines covered

The 6G72 DOHC is a 3-litre V6 with four valves per cylinder and two camshafts per head. Mitsubishi fitted it to the 3000 GT, first naturally aspirated (Z11A), then as the twin-turbo, four-wheel-drive 6G72-T (Z16A), sold in Japan as the GTO.

The engine has 12 inlet valves, originally MD135481 and later MD135479, with a 35 mm head, a 6.6 mm stem and an overall length of 106.28 mm. More boost, sharper camshafts or a higher rev limit put each of them under greater load every time it opens.

FERREA and SUPERTECH reinforced inlet valves

On a 24-valve V6 that loves revs, every inlet valve opens and shuts several dozen times within a second to meter the incoming air. Its head slams back onto the cylinder head seat at each closing, and its stem rubs relentlessly inside the guide. The working range runs from 400 to 550 °C, a zone in which plain chrome-silicon steel already gives ground: 500 MPa at 500 °C, then 250 MPa at 600 °C, just beyond it, meaning 50 % less strength. Higher boost, sharper cams or stiffer springs make those impacts, that wear and that heat worse still.

Both brands offer valves in a race-quality chrome-nickel stainless from the EV8 family, which holds 650 MPa at 500 °C and 550 MPa at 600 °C: 30 % and then 120 % better than the original steel. FERREA supplies its Competition Plus range here, chromed-stem stainless for which it claims 20 % extra hot strength and fatigue resistance plus 25 % longer seat life. SUPERTECH treats its stainless with black nitriding: the surface becomes harder and smoother, and the stem wears less as it slides in the guide.

The +1 mm oversize takes the head from 35 to 36 mm, leaving the stem and length alone. More air then flows past the seat, so the cylinders fill better and power rises, as long as each of the 12 inlet seats is opened up to suit.

Inlet valve technical specification

F1851P is standard size; F1852P and MIVN-1012 are +1 mm.

Fitting details

The collets, original MD016483 or K10035, must match the groove of the chosen valve: check this before compressing the springs.

With the 35 mm head the inlet seats keep their factory size; with 36 mm the workshop machines all 12 of them.

The 6G72 DOHC operates its valves through rocker arms with hydraulic lash adjusters: there is no valve clearance to set after reassembly.

Technical guide

The brands offered

	FERREA Racing Components started out in Fort Lauderdale, Florida, in 1978, set up by two engine builders who came from Argentina, and keeps production in house. Its single-piece valves are forged from bar, fully CNC finished and raced in NASCAR, drag events and on circuits.
	SUPERTECH, from its San Jose workshop in California, has developed racing valvetrain components for over thirty years. Each valve is created for one specific engine, goes through ultrasonic testing, X-ray imaging and laser gauging, then proves itself with tuners from drag strip to track.

How to choose

On this V6 two criteria separate the sets: the size, depending on whether the inlet seats stay standard or go to 36 mm, then the material and finish.

When reinforced valves become necessary

• Bigger turbos or raised boost pressure
• More aggressive cams or stiffer valve springs
• Rev limiter pushed higher
• Head rebuilt for track, drift or drag racing
• Mitsubishi valves worn, marked or seats already recut

Compatible vehicles

OEM part number (inlet valve): MD135481 then MD135479 (6G72-T); MD135479 (6G72)

Related products

With the 6G72 heads off, it is the right moment to replace all 12 exhaust valves too, which we offer in reinforced form on the page below: