I want to dogpile on the no thermostat means the water goes too fast and doesn't have time to cool misinfo.
Yes, if ti passes through the radiator quicker, it has less time to dump heat. But at the same time, it doesn't stay in the block to gain as much heat either. The faster it circulates, the more BTU's the coolant can POTENTIALLY carry away.
Here's a tasty little trick to add to your idle cooling issue.
https://www.ebay.com/itm/12377961269...3ABFBMlKbqpolh
When I was a kid and got my first car, I studied everything in the service manual, including the hydraulic circuits in the automatic transmission and emissions BS. This little valve is to keep hot idle temps down. When the coolant temp passes 200 degrees, it switches the car's vacuum advance from ported to manifold. This bumps idle timing up from the typical 10-12 degrees to more like 18 where the engine will idle faster and much cooler. In the auto dark ages (mid 70s to 90s) they ran idle advance way later than an engine really likes to keep the catalytic converter hot enough to work.
Someone maybe 10 years back wrote a big dissertation on timing, and it's worth digging up and reading.
As for me, I have a 427W with megasquirt, and the 16" spal fan and a $100 fleabay universal radiator, and the only time I had a minor heat issue was wen the fan relay melted down. Megaquirt's timing map has no load idle around 16 degrees, dropping back to 13 at the top of the map.