RoadSpike

Wow this has been answered quite a few times

These engines are aluminum blocks so obviously more metal around the cylinder wall is required unless you wish to put in stell inserts

Here's a picture of an open deck (ej20t for example)

Semi Closed ej25t


The fully closed deck


Sleeves being installed (axis monster 2.65l)

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funkdrmr

First off, you can't necessarily think that because a block is closed deck you can just up the boost & go. Your tuning could blow a built closed deck block just as easily as blowing up your stock motor. I know nothing was mentioned of this, but I like to point it out as it's something that a lot of people seem to take for granted.

The difference in closed deck / open deck doesn't have to do with the cylinder heads. It has to do with the deck surface. This is where your cylinder heads mate up to your block.

An open deck block will have more area around the cylinder where the coolant flows (watter jacket). A closed deck block will have less area around the cylinder for the coolant to flow.

The advantages of a closed deck is that the cylinders will be stiffer, therefore more able to withstand higher cylinder pressures. It also keeps the cylinders from moving around as much during high loads. An open deck block would be more likely to have the cylinders move around under those loads, causing rings to lose their seal....bad stuff.

I'm not sure about the rest of your questions, but I'm sure someone else here can chime in about the material and Mitsu question. For some help, here's some pics of open, semi-closed, and closed deck blocks from Cobb.








Also, check out this post: https://www.i-club.com/forums/showth...&threadid=6241

I found the pics there, and there is a TON more information there than I could offer you.

funkdrmr

Crap, RoadSpike beat me to it!

RoadSpike

Thats ok i like your pictures better