I just want to ask if my 4k engine will increase power if i will put 3k pistons(highcomp) btw, my engine was ported and polished and shaved head.

whereabouts are you josh? I'm in toledo , cebu.

u need to let the guys here know exactly which 4k u have, but even better still, because of all the rebuilt motors here in the philippines, u really need to confirm which pistons are actually in it now. 

Mine is a 4kU which happens to be quite popular here, with the D shape dished pistons. have a look with a flashlight down ur spark pkug holes and see if u can see a dish on the crown.

i believe u should get a bit better compression from flat top pistons but I'm not sure that it would be worth it unless you allready plan to have the engine apart.

whatever u do, make sure you change the spark plugs to suit the new flat pistons.

I think 3k pistons in a 4ku would give you too high of a C/r