When you sleeve a block, you can sleeve it wet or dry. The reference is to whether or not the sleeve is in direct contact with the water.
If you dry sleeve the block, you would basically just be boring it out large enough to eliminate the factory liner and into the aluminum, then you would press in a new, stronger/thicker sleeve.
When you wet sleeve it, you install sleeves that are so large, they are in direct contact with the water around the cylinder. In the VQ, this means removing the entirety of the floating sleeve. Then you press in the new sleeves.
A wet sleeve process is an interesting one, because you go from a block that was essentially one complete unit, to a block that is now just a chassis for individual sleeves that are just resting inside it. You have sacrificed some overall integrity of the foundation for the sake of individual cylinders that can handle much more pressure.
For a VQ block, this sacrifice is minimal since the sleeves were floating anyway, you remove very little of any structural part of the block. You are also adding some sleeve stability since the wet sleeves contact the block horizontally at the deck, when the stock sleeves last touched the block at the base.
There is lots of argument back and forth about the potential side effects of large masses of dissimilar materials when you put these giant ductile iron sleeves into aluminum blocks. There is no argument that the wet sleeved block will hold a LOT more power than the standard VQ block. The argument is to longevity, most specifically the headgasket.
Attached are photos of a VQ37VHR block prepped for a wet sleeve install, and a wet sleeve before installation.
If anyone wants a wet sleeve setup, I am practically next door to the guy who does the wet sleeves for most powerful GT-Rs, and as you can see from the photo, he has VHR experience as well now
