Evo 9 head is known fir warping when ported?

Did anyone come across the issue of evo 9 head warping when installing oversized valves and porting? I was told that it is a common issues...

Not aware of it being a problem for any cylinder heads, let alone a 'common' one for a specific engine - not saying it can't happen, just not aware of it.

Do you have personal experience of this happening, or is someone trying to sell you a warped head?

I already bought a used evo 9 head and been planning to drop in oversized valves and do some porting to it but one guy advised me no to do so as he is running a mechanical work shop and he experienced that as a common issue when people bring ported evo 9 heads or heads with aftermarket valves and find out later that there is some air leaks due to head warping. According to him the reason behind is the additional mivec oil channel in the head that makes it less strong than evo 7 or 8 head. I have personally never heard of that despite being in 4g63 community for almost 15 years but he is also quite experienced in that business and i would never think it is something he is just making up ...

To clarify, in case it's a translation problem (although your english is VERY good), do you get the impression he's talking about the head gasket surface warping (which could have been due to overhheating or other issues) and head gasket leakage, or if he's talking about internal leakage through the waterjacket, ports, and/or oilways (which may be due to 'amateur' DIY 'porting')? Something else may have been if they unbolted the head from one end to the other, especially if hot, or used excessive prying to separate it from the block?

The only heads I can think of, off hand, that had a known casting problem were the later German/GM castings for the GM 20XE engine which were redesigned for cheaper manufacturing, and could develop an internal crack between an internal oil passage and the waterjacket - the early COSCAST ones with a different design were fine. This wasn't a 'warping' problem, though.

Any head might have problems if severly skimmed, though, I expect.

As you say, if there was a known problem, I would have expected you to know about it - A quickish look on the interweb doesn't seem to have come up with anything.

He was talking specificly about combustion chamber not being sealed property by valves as they come out of proper seating position because of head wraping in case of high boost applications... Gasket sealing is not an issue but valves proper alignment is and that's what causes the internal leaks. He reckons that it is not an issue on previous evo model heads as they have a bit more meat on them and that is just enough to make them withstand much bigger abuse comparing to evo 9 head...

Would it be possible to cut the larger valve seats with a "reverse torque plate" so the head has the same hold down forces applied, or are people already doing that?

It could be, Georg, if there's been enough material removed. If it's happening, it could also be due to thermal stress - the heat passing through the head differently and so having different expansion rates in different parts of the chamber, rather than an inherent weakness. Ah, on that, I have found some mention of the coolant passages being different to accomodate the MIVAC... Same result, though.

In extreme cases, either problem can even result in the seats becoming displaced or even dropping - but that's more common with poorly installed aftermarket seats.

Come to think on it, it could also be partly due to using oversized valves on the OEM seats, with the seat inserts being thinned too much, when oversized seats really should have been fitted. The inserts are actually rather rigid, but if too much material is removed they could be distorting slightly?

As you said, you (and many others here) have a lot of experience with the engines and know many others who are working on them, so would have expected you to have heard about this before if it'smore than just this chap experiencing it.