i had the same problem,rad did not have good flow and slowed the whole thing down,i used two pumps one for the rad and one for the block and that will work.now on my next home made job i am useing the reservoir made out of large heat sinks 8x6 3 inch fins,i just tested my new 3x2x1x copper block that i made on a 1900 watt hot plate set to 400F after 30 min water temp went to 107F with no fan on the reservoir,i think it will handle my system just fine.so i have 2 pumps and no rad to slow down the flow.
