I want to get high compression pistons, what bore size and compression ratio would work without any mods to the connecting rods? what size head gasket do i need also?
I am using 81.0mm bore size with 11.1:1 compression pistons (flat with valve cut). From Wiseco also. I also shaved 2.5mm off the head of the ECOTEC.
I feel compression can be higher than 11.1:1, maybe 12.5:1 would be better. (dome with valve cut).
But pls change the gasket to better one, cometic if possible from the source you quoted.
If budget allows, maybe you can get these stuffs which I am using . Forged con rods (H Beams with ARP bolts) and Performance Head Studs. Camshafts 275 degree durations and lightweight camshaft pulleys. Lightweight crankshaft pulley. Aluminium thermostat. New timing belts, coolant pump and idler pulley and tensioner pulley. 4 to 1 exhaust, 2 inch straight through.
New crankshaft bearing and new con rod bearings is a must.
With all the above and AEM cold air intake, I am having 146hp. So maybe you can take that as a reference. If not good enough for you, maybe you can try turbo charging. Many aveos are getting 200+hp easily. But pls get forged internals with 8.5:1 pistons or you risk blowing your engine.