If you dont have a thermostat, the coolant never gets a chance to slow down and pickup heat. PUT A THERMOSTAT IN THE ENGINE. Yes, thats yelling.
Your builder should be ashamed of himself. restrictor orifice or a thermostat with bleed holes would be the only bypass devise to use. Not go without a thermostat.
I asked my 86 year old step-dad who owned and operated an automotive machine shop for 40 years (closed it 10 years ago because of all the electical/computer crap as he put it on cars). He told me it was not uncommon to not put a thermastat in the older engines but the newer engines you have to, so the engine will run at the right temp. He also said if the engine was not running at the correct temp +/- a few degrees that you will start to see more problems down the road
