heats up and wont cool down

Yes i agree it could be the thermostat, but Baril (engine builder) thought that when they had it, we changed it to a new (unfortunatly a stat 192 all they had), did the same thing, so they are stumped too, i've read posts about others with heat issues and some guys dont run shrouds and they dont have heat issues, I know each engine is different too, I am running cast iron heads, 202's and 165's port matched, bowl blended, but nothing too radical. Comp cams #279TH7 Thumper flat tappet cam, 242 dur 488 lift,