When I got my XC3 block back in Nov EKWB instructions had you putting 1.5mm thermal pads on them but they didnt make contact with anything.
Emailed both EVGA and EKWB support about it. EVGA emailed back first and said they are cooled from factory so they should be cooled when using a waterblock since they will have reduced air flow. (Makes sense to me).
EKWB reply was that I could return the block if I wasnt happy with them not making contact.
I forwarded them the email from EVGA then they said they would update there install instructions and include 4.5mm thermal pads from now on.
Few guys on the EKWB facebook that got later revisions had theres come with those pads,
Either you got old stock or they decided to cut costs and not include them again. (Which is stupid since the block has the recesses cut for them)

XC3 block and back plate have other issues as well.
Back plate will short out the back of the fan header pins if you dont space it out further.
Contact islands on the back plate are in wrong place for the vram by couple mm (not issue for 3080 obvously)
Stand off areas on back plate are all different heights so when done up tight you can see the backplate flexing (Also amplifys the coil whine since it allows the whole back plate to buzz on the stand offs that are shorter) EKWB fix is to losen all the screws if you complain about it.
Standoffs around the die are all different lengths giving you bad contact on the die if you dont skim them down.
Deep CNC machine marks all over it and the whole contact area is very unflat.

Bit of a shame really since 1080ti and 2080ti EKWB blocks were top quality where there 3080/3090 blocks are the worst quality of all the blocks out on the market.
 

joder
So I put my XC3 under water yesterday and the temps are great as one is to imagine.
 
When taking off the stock cooler I noticed that lovely thermal putty that was on the inductors / chokes.
 
The EKWB water block instructions had no mention of covering these areas with thermal pads or putty.  I thought that was quite weird but went on my way anyways.  Fast forward to today when trying to run a few benchmarks for fun.  Before I could got over 100% power and over stock voltage and not have any issue at stock clocks (I could even get +150 on the GPU) with the stock cooler.  Now, I notice that I can't go over 100% at all even at stock clocks or TimeSpy will crash.
 
I would like to know the official stance from EVGA on cooling for the inductors/chokes.  I would assume there is a good reason that they used thermal putty on these?  I've seen things saying that they don't get that hot and can stand the high temps as well as the putty is there to reduce noise.  Not sure if this is true and the only reason for the putty?
 
 
 
 

 I redid my thermal paste and the Thermal Grizzly minus pads I had happened to be the perfect thickness. You do need something there. If the block is close enough perhaps paste will work?

Anyway look into those Thermal Grizzly minus pads, you can cut them to size and they're very reusable as long as they don't get squished too much.

 
That's pretty bad (first 2 posts in thread). I wonder if the FTW3 blocks will have any of these issues.
 

xxDarkxx

 
this is what i did
 
wiped off all the putty and used fujypoly

What size pads did you use? 1mm and 2mm?