Valve Face Thermal Coatings

[BOOT]

How does it hold up? Does it last on the street or is it only really for a frequently serviced a race car?

[Momus]

Apart from CrN on titanium valves, does anyone knowledgeable use valve face coatings?

[6.50camaro]

DV touched on this subject in his head porting book. It was near the back of the book, chapter 11 page 137. Dan

[BOOT]

DV touched on this subject in his head porting book. It was near the back of the book, chapter 11 page 137. Dan

DV has mentioned it many times I'm sure, saw him say it in an older video a few years back(80's or 90's from the quality if my memory is right) and again in one of his recent youtube ones I think.

But DV deals with race only stuff sometimes I think, so idk if it can be applied for street-ish builds.

[David Redszus]

What would be the intended benefit of valve face thermal coatings?

What problem are they intended to solve?

[PRH]

I’m guessing the issue here is the term “valve face”.

Maybe I’m wrong, but I think the OP is referring to coating the side of the valve head that’s in the chamber.

[In-Tech]

I’m guessing the issue here is the term “valve face”.

Maybe I’m wrong, but I think the OP is referring to coating the side of the valve head that’s in the chamber.

I am in agreement that it must be a nomenclature mistake. I don't know of any situation where the seating surface would want a coating, how are you going to get the heat out of the valve if coated? The Ti stuff does wear a bit even with copper/beryillium seats but shoot, I haven't kept up much so maybe there is some stuff the high end guys are doing?

[6.50camaro]

What would be the intended benefit of valve face thermal coatings?

What problem are they intended to solve?

According to DV in the book. He was taking photos of a 2.0L Cosworth Midget engine in the dyno room running at 8500 rpms. Happen to look down the intake tract and see the intake valves glowing a dull red. At that point he said it never accrued to him how much heat the intake valve absorbed and transferred to the intake charge. Ater coating the intake valve face they no longer glowed red and the HP went from 280-281 up to the upper 280's. Just relating what DV wrote. This took place around the early 90's. Dan

[PRH]

Sometimes its not crystal clear what one is talking about......

A2122CD2-DDDA-418E-8948-1ED2D4C4EA77.jpeg

[stealth]

Lots of valve seats get coated...Nascar valves.

I've seen some DLC coated seat too....

valve.PNG

valve.PNG

[BOOT]

Ok ok term Nazi's LOL Long ago I was taught that the Head is the Face of the valve and it's stuck in my brain that way. I know some get confused because of the Seat-Face and that is part of why I started over on a video because I put Face for the Head on the board. Knew it would catch the Nazi's eyes LOL
https://youtu.be/aTj1j28mWdk

It's not the only component in a MOTOR has that goes by diff but sim names. Now can we get back to the subject or shall we waste time on terminology.....

[BOOT]

Lots of valve seats get coated...Nascar valves.

I've seen some DLC coated seat too....

Not what I meant but cool!

[David Redszus]

Much depends on the materials being used and/or the problem to be solved.

When NASCAR first tested unleaded race fuel, they had a severe valve recession problem.
They were running titanium valves on copper/beryllium seats. They only lasted about 100 miles using
using unleaded fuel.

The titanium would micro weld to the seats, then pull metal out when the valves opened.
Two solutions were possible. Either go back to leaded fuel or find some other valve/seat combination.

The problem was the result of overheated valves and uncontaminated seat contact area.

A quick look at the thermal conductivity of various metals told the story.
Titanium - 4.2 ..BTU/hr/ft2/ft
SS 304-- 9.4
4130-- 25
The poor thermal conductivity of titanium resulted in very hot valve seat surfaces which
resulted in the micro welding.

The use of leaded fuel could not be considered due to the new green rules.
The alternative metals with higher thermal conductivity were considered too heavy for
the rpms they needed.

The solution was to coat the titanium valve seats so that they would not micro weld to
the beryllium/copper seats.

Ceramic valves were also considered but rejected. They provided a very low thermal
conductivity so that the valve face would overheat causing pre-ignition/detonation.

Interesting that loose engines that allowed oil into the chamber did not have the problem
since the oil provided a contaminated surface junction that prevented micro welding.