Onemangang, I have an engine that's been plugged, decked and redrilled as you've stated. Although the engine isn't a typical one for the street. It's a Rodeck Aluminum 350 plus block, identical to a SBC. I have no heating problems. Something I ran into when I got it running, I had to drill bleed holes in the Thermostat, to pull heat into the intake manifold so the temp sensor I'm using for the fan controller would work properly. Hope this info helps.