[scottj]

Guys,
What I described, when used with a high-flow pump and a high performance (30-31 psi) radiator, would be an optimal system. With that system, water pump pressure is not “excessive”, but desirable. The system is designed to run the highest pressure that the radiator will allow and the highest velocity that the water pump will generate. Higher velocity transfers heat more efficiently, because of increased turbulence, in both the radiator and in the engine. The higher velocity also aids in “scrubbing” hot spots, which cause detonation, from the cylinder heads. Higher pressure transfers heat better than lower pressure and raises the boiling point.
Running a 1qt surge tank on the low-pressure side of the system is the optimal location to separate air from the coolant. That location has the lowest pressure and lowest velocity in the system. Under those conditions air will separate from the coolant more efficiently and expel from the system only when total system pressure (unaffected by direct water pump pressure) is exceeded.
This idea behind this system is contrary to the idea of running under drive pulleys and restrictors to slow the coolant down. The old vertical flow radiators couldn’t use a surge tank so those were necessary means of keeping coolant in that system. A low rpm (street driven) surge tank system should probably use over drive pulleys to reach maximum pressure and velocity. When the cap is in the high pressure hose, the tendency is for the water pump to push coolant out at higher rpms and as a result, reduce the effective “safety factor” that the cap could provide.
If our cars had the radiator positioned higher than the engine, we would all be running radiators with the cap on the top of the low-pressure tank and not even thinking about it. Since we can’t, the surge tank will do the same thing and I would take the position that this is the proper system design.
Scott