i use 160 degree and 4psi in my 53 gmc 228 and it works great. keeps it almost constant 185 even in 100+ degree weather with the heater core circulation off.
tony

Overland Blue, 1953 GMC 1/2T, 100-22, 228/1bbl, 4sp/4.10 6v, shortbed/fender side/5-window.