Engine Block Coolant Plug

[L31MaxExpress]

The cooling system should be running about 10-20 psi when hot. The factory radiator cap relieves at 16 psi. Even considering fluid dynamics, 100 psi under the heads sounds like a tall tale to me.

A properly functioning cap has the inlet side of the pump at about 16 psi, even a stock pump moves ~60 gallons per minute. A 19 psi cap will make the stock pump move even more water due to less cavitation. The pump takes about 10 hp to turn at high rpm. The coolant passageways in the head gasket are fairly small and flowing 30 gallons per minute through them which equals back pressure to flow.

A nascar was instrumented for flow and despite the massive underdrive they run on those pumps, at 9,200 rpm engine speed, water pump turning roughly 1/2 speed they saw 102 gpm flow from the Stewart pump they were running.

 

[Schurkey]

The big advantage to cross-flow radiators compared to vertical-flow, is that the pressure cap is on the suction side of the water pump. The system pressures increase from there.

 

[L31MaxExpress]

The big advantage to cross-flow radiators compared to vertical-flow, is that the pressure cap is on the suction side of the water pump. The system pressures increase from there.

I agree and with higher system pressure comes less cavitation and more flow.