Can this cause engine to overheat?

I had my cylinder heads skimmed & new gaskets : I did not re-torque the heads again can this cause engine to overheat under hard acceleration only heats mostly uphills & under a little hard acceleration: but at slow speeds, traffic the heat gauge sits at quarter. All water related parts been fitted brand new. My heads have not been re-torqued & if the tappets are not set correctly can this also cause over heating, thanks