I have a brand new usdm sti shortblock that i am going to put in my 02 wrx. i am going to use the wrx heads. the first thing that i noticed is that the sti block has a port of some kind coming out of the top of the block. it would be under the throttle body if the intake manifold was on. Is this a coolant passage? do i need to use it? or can i just plug it? What else am i going to need for this block swap? i have thicker cometic head gaskets already and arp head studs. what else?

You might want to move this thread to 2.0L or 2.5l youll have more peps see it

i can answer this, as i went through the same thing. the 2 ports coming out of the top of the block are for breather hoses that would normally run into the avcs heads. they spit oil. since you don't have avcs with the wrx heads, you can do one of 2 things, either a) cap the ends of them, or b) modify the black ports on the top of the heads where the breather hoses on the wrx originally go in to accept 2 hoses. that's what i did and it worked great.

cometic head gaskets are a good idea to lower compression to 8:1 like you said; while arp studs aren't necessary it's not a bad idea. i was using both.

get engine management or else your setup will go boom.

sounds like you have what you need to have a good running motor. do not use a td04 on it though (wayyy too small).

any other questions? i have lots and lots of experience with the hybrid motors, so pm me.

so with this swap you want to keep the compression around 8:1 (w/cometic head gaskets)? not the 8.6:1 (w/stock ej257 gaskets)