First off, not a stupid question
NA subie engines are not as strong as the forced induction ones.
The NA subie engine is an open deck. The WRX and STI blocks are semi-closed decks (I believe this describes the way that the heads connect to the block and the way that the coolant flows around them....or something like that...i'm not a turbo block expert)
Basically from least strong to strongest....the order is the open deck (2.5i), semi-closed deck (08 WRX, 08 STI), closed deck (older wrx engines (some EJ20s in JDM legacy/WRX, EJ22 found in the 22B impreza)
For us, this means that the NA engine is just not as strong for holding boost (or increased compression) without modification.
Subie NA engines with turbo kits can only somewhat reliably hold around 5 PSI of boost with a 10:1 stock compression ratio...more boost is possible with lower compression turbo pistons.
Depending on what you take your compression ratio to 11:1 or 12:1, you may need to upgrade some internals, but you may not.
The best way to find out is to ask the piston manufacturer, they'd know for sure.
In my opinion, if you are breaking your engine apart for higher compression pistons, you might as well swap in some stronger parts (better headgaskets, stronger head studs, rods, maybe a stronger crank shaft.) It's not going to hurt anything and if you swap in high quality, stronger parts, it should definately not break.
I'd rather do it right the first time and not have the engine blow apart or start leaking and have to redo or replace things
***Replacing the internals of a subie NA engines will give you decreased engine longevity and you'll definitely require a tune then...NA subie engine building can (but not always) be a money pit, beware!
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