The issue with sleeves is your removing more wall thickness, which is already not strong enough.

There was also something about some gen3 blocks having uneven wall thickness due to a manufacturing defect.

I believe over the years with the revised blocks the material has improved.

Be interesting to see how well a caldina block holds up. I know of one punching out 300+kw iirc. Keen to see how long it holds together.

^ my point exactly. Was confused with Dart & Darton. Let me know how the Darton sleeves work out for you.

if you keep to minimum over bore (86.5mm) pistons i think the 3s block is fine provided (as with everything) it's spec'd and put together by a compitent machanic and then tuned with a capable ecu with reasonable saftey margins.
 
and then treated with respect by the owner.
 
some people have no mechanical sympathy and then wonder why stuff breaks.

just_ace
The issue with sleeves is your removing more wall thickness, which is already not strong enough.

Yeah you are removing wall thickness but replacing that thickness with better stronger material. Thats the whole point in sleeving the block. Removing the weaker factory material to replace it with something stronger.

but what stops the weaker material that you've made thinner from cracking? which as i understand is what still happens.
 
i think someone even tried filling in the water galleries then boring them to mimic the 5s block, but for whatever reason it didn't help.

The idea is that the sleeves strengthen the blaock so the heat transfer and stress on the weaker material is less. Much like placing a soft piece of metal on the ouside of the block like aluminium. It wont break but stick it inside the cylinder wall and it will be destroyed....

Not having a go at you mate, but just_ace and MR2QIK are right.  Sleeved 3s blocks are prone to cracking too.
 
A few different reasons...some even partly to do with the configuration of the engine.  They may be stronger just at the sleeve (compared to the cast) but the problem is when adding boost and more fuel, the sleeve expands at a different rate to the block. 
Two metals expanding at different rates = problems. 
Also, keep in mind the torsional stress on the block on launch due to its configuration.  The casting is weaker due to the amound of material removed to fit the sleeve, and so can lead to cracking.
There are other issues too with sleeving - the top of the sleeve can expand and push the headgasket and head upwards, leading to headgasket fail and cooling issues.
 
TB Developments in the UK have actually found that on their drag research car the sleeved blocks have always failed before a normal run of the mill gen 3 3sgte.
 
However, if you do go down the track of sleeving your block, let us know how it goes - am also keen to see how the Darton sleeves hold up :)

Sleeves wont help the cracking around the water pump

Yeah I wouldn't use sleeves in a 3SGTE.  Closed deck, cast iron.  Either run it with minimum underbore or go 5SFE.  Saying it'll crack over x psi is absolute bollocks, there are far more variables to be considered.  Least of all that 16psi will result in different cylinder pressures and thus power output on different turbo or engine configurations.

I'm just referencing what I was told through Neil Bates racing when I spoke to them. The pistons I've got are 86.5mm but I'm only doing the engine rebuild once mine lets go which hopefully doesn't happen anytime soon. I believe they refer to 16psi just as the bases for power output. They weren't saying about cracking at the water pump, from there race experience cracks happen between cylinders 2 and 3. As for the seal up top most places suggest o ringing or step machining. I didn't get into that detail with engine builder though was just after a price quote, which wasn't too bad actually.
Personally for me I've spoke to them and another engine builder who also said the same thing. Before I do my build, if I ever need to I'd give a few other places a call like some of the drag shops out of the states to get there advice. Based on what all of them say I'll go with that. Something worth considering though as I don't think anyone is disputing that the 3S blocks are prone to cracking. I didn't actually know about it till I called Bates about something separate then they asked what boost I was running and it went from there.