Please forget your preceonceptions.
I am quite willing to do without any blunders occurred in which I am, nonetheless those "preceoceptions" are just results of some direct observations: I am quite sure that I have may done some errors, but unfortunately I don't see which they are.
I have already stated how you work out the heat capacity of an object, the mass of the object is a term in it. With the Orochi you have a massive heat capacity. If it was no good at radiating the heat, that would be a different thing, it would take ages to heat up but carry on getting hotter. That is not happening. The Orochi does not heat up. Your CPU is not in good thermal contact with it.
Those results told you so, and that's ok: but I have no evidence where the problem lies.
I saw that the cooler worked at stock, the TIM footprint is at best lacklustre but it is still not indicative of any lack of contact, the heatpipes and the base doesn't look compromised, the CPU has no problem at all, so you (and Vicotnik, and xan, and Steve) may be quite right there's a a no good thermal contact, but I haven't seen what/where/how.
You said it's not important that I didn't see that, but it did matter *for me*: if I don't know what I have to correct, I cannot solve the issue. Well, actually I've solved it: I put a Hyper212 on that Core i7 and the Orochi into the box.
Things to try:
1. Check the temperature of the cooler during operation. 50C feels hot to the touch so if the cooler stays cool then it is in bad thermal contact.
2. Try with the case lying down flat so that the cooler isn't putting excessive moment on the CPU socket. The Orochi is very heavy and if the weight of the Orochi is the problem, this will resolve it.
3. Try with another CPU cooler like the standard Intel cooler. If it is still bad then the cause could be the heatspreader coming off the CPU itself.
As stated in previous posts, either these things have been already done or they are not relevant. Thanks anyway for support and patience.
Even if you want to look at the Orochi like a two-stage cooler, then the "base" heatsink close to the core should be very, very hot if contact is good. I don't think it is.
Vicotnik, all of you are persuading me that there actually was a contact problem, even better, that only a lack of contact may explain a quick shutdown.
Just FYI the secondary heatsink was hot, but not "scolding hot", probably it has been around 50°C, probably something less.
At any rate, the mounting mechanism is error-proof (you have just to screw in from the backplate towards the retention brackets unless the screws stop), the cooler was clearly leveled (no screw looked anyway "longer" than other above and below the brackets threaded nuts), the Arctic Silver 5 is known to not work at its best when freshly applied but however it works, the TIM footprint was not so good but it's similar to the one you get from several other coolers which give sub par results (but not shutdown: such as, again, Ninja 3, Dark Rock)... so, when I will have some spare time, then I will take out of the box the Orochi again, in order to test it "better"... och tack för nu!
this has me stumped. i see no reason why orochi cant handle the heat.
Me too: that's why I picked it.
grasping at straws here... -could rapid heating of the spreader and cpu hold down allow the cpu to lose good contact with the heat sink, but return to normal after cooling off??
I can't help: anyway, the hold down tabs are about perfect, that effect you see it is just a matter of the photo perspective.
edit: and in pic two i swear i can see the indent of the hold down tab in the tim on the base of the heatsink.... i wont say on which side yet, so you all can see if you are seeing it too.
I see no indent.
clearer pics would help...
As said, after two days testing I put aside the Orochi, I put the Core i7 back in its rig and bolted a CM 212 onto it: so there are no more pics. When I'll have spare time, probably I will try to take better shots.
Thank you anyway for your interest and help.