Adding fluids to hot valvetrain

[Klutch9]

A similar topic has been covered before, but it was regarding hot engines. Some engines, however, have oil fil tubes that drop right to the crank case and never touch the valvetrain. So, is it bad to add cool or room temperature oil/additives to a valvetrain that is at operating temperature? I know all about "thermal shock", but I'm wondering if adding room temperature oil to a hot valvetrain would even be enough to do this.

Back at a shop I used to work at, we would punch a square tube, 1/4" thick-walled, into a die and it would come out glowing red, ~700 degrees F. We would then immediately spray it with COLD water until it could be handled with gloves, or to about 100 degrees F... that's a drop of about about ~600 degrees over the timespan of less than 1 minute and those tubes never cracked. As an aside, water also carries/distributes heat better than oil does. So I'm guessing that adding fluids to a hot valveteain won't hurt a darn thing. I just wanted to make sure, because I may have done this yesterday... with some Mos2...

 

[45ACP]

It should be fine.

Its cold WATER on a hot RADIATOR that cracks blocks and things like that.

The oil heats pretty much instantly if coming from room temperature to a hot engine.

 

[Klutch9]

Even though the oil is cooler than the valvetrain, like you said, the oil itself will heat up pretty quickly (although not as quickly as water would). However, I don't think that the oil would drastically reduce the temperature of whatever surface it touched, since that surface, say, a camshaft labe, is connected to and surrounded by so many other HOT parts, that those parts would keep the camshaft lobe, which came in contact with the relatively cool oil, still hot, and prevent shrink and/or expansion damage.

I like to imagine what happens to a bone cold engine, when it's 0 degrees F outside, and you crank that engine and combustion starts inside that engine. And we all know how HOT combustion temps are... yet, I have never seen an engine valve, spark plug, or piston crack from that incredibly drastic and instant change in temperature.

 

[A_Harman]

The upper part of the valvetrain; cams, rocker arms, buckets, valvesprings, etc, will not be operating at temperatures exceeding ~350F at any time. Every steel component in there is heat treated during manufacture by heating to 1650F, and then quenching into agitated oil. The thermal stresses caused by pouring room temperature oil on valvetrain components that may be at 350F (at the most) are puny in comparison.

 

[Klutch9]

That's a good point. I knew that the valvetrain components were heat-treated, but I wasn't sure on the process or how they were cooled afterwards. Thanks!

By the way, your answer, A_Harman, was far better than any I could find on google after a lot of searching.

 

[440Magnum]

Oil has drastically lower heat capacity than water, so it transfers heat away from hot metal MUCH more slowly. Thats why cool oil is used to harden metal just removed from a forge at nearly 2000 degrees F, whereas water would shatter it.

There's no way pouring cold oil into an engine with components that are *at most* 300 degrees F (and that's if its running seriously overheated) will do harm.