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Curious George
'99 LX Civic Sedan
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Discussion Starter #1
This is a pics on my oem valves, I cleaned and polished them little bit, and black coating isn't there. So, does it has chance to hurt something later like burning a valve or anything else like that ? I don't know if oem balck coating worth, or only to rust protection ?

Take a look.
 

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1997 Civic Hatch D18Y8 M62 S/C
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You know, I've wondered the same thing. I have a number of wild guesses as to what benefits the coating provides.

1.) Rust protection could be one and would seemingly only come into play when the engine's been sitting for a while, otherwise the oil and carbon buildup should retard rust. Maybe more effective against rust on the intake side where it's exposed to moisture.

2.) Heat shielding (as you suspect). It doesn't seem to me to provide much insulation or deflection. Valves dissipate heat into the head when they contact the seat.

3.) Carbon buildup prevention. Does it provide a non-stick teflon-like surface? It doesn't appear to be effective to me since most used valves I've seen are loaded with carbon. While I've never seen stainless valves in person, the pics seem to show no coating.

4.) Does heated oil have some long term detrimental effect on bare steel?

Just guessing here. Any experts?
 

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Curious George
'99 LX Civic Sedan
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Discussion Starter #4
I don't know if it's oem nitrated, but stock valves are black coated.

I will let those valves shined like that, and I will see next head removal state of everything.
 

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Just got off the phone with my friend from ARIAS... He said that polishing the valve is ok but not the stems. If you polish the stems it may leak oil through the valve guide seals.. Other than that there wont be an issue.
 

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blk92 & belette are correct.

the valves are bath nitrided, which leaves a black finish. this is actually meant for the valve stem- hardening it and reducing wear. so removing it from the valve head is ok.

bath nitriding is as effective as chrome plating (more common in the US)
and chrome plating reduces stem wear 80% over 50k miles.

also valves are normally a combination of a stainless steel head (notice its not magnetic- due to its low ferrous/ high nickel content) and a high carbon steel stem.

the coating would not be used as a rust preventative as higher grades of stainless steel do not rust.
 

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Curious George
'99 LX Civic Sedan
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Discussion Starter #8
but do you think that valves without coating will burn or wear soon ?
 

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I was told that it will be fine. Not an issue.. :TU:
 
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