if I change to vortec heads ....should I stay with 76cc chambers? because right now I have a hard time running pump gas..I need premium or it pings from low octane.....I was told I had around 10 to 1 or 10.5 to 1 compression with the flat top pistons and shaved heads..Is that true? I am not sure how to calculate it...anyways....what size chambers do you guys recommend I get and still be able to run pump gas

thanks again