Reading this technical discussion for a proper cooling system has me wondering why my cooling system works. What I have on the Lakester comes from years of using something similar on road racing cars. One simple feature was to keep the swirl pot (header tank) higher than the cylinder head/radiators and drilling a .125" diameter hole in the perimeter of the thermostat, all to bleed off trapped air. In a road racing car, it was often difficult to position the swirl pot higher than cylinder head but much easier in the lakester (see images). Also, I use just a 7 pound pressure cap on the swirl pot. BTW, my radiator is contained in a five gallon water tank.
John
Hi John,
Well if the swirl pot and or expansion tank is higher than the cylinder head and radiator, then many potential problems are averted. Any trapped air collects at the highest point in the system, SO . . . . . . .
Systems where the cylinder head is the highest point can work:
A/ With a complicated air purging sequence as the system is filled. The problem with this is: that if a slight overheating condition is created and there is no effective coolant recovery, the head gets cooked.
B/ Use of a pressure bleed system. The problem with this is: it is complicated to plumb, and can be tricky to size bleed orifices. BUT, coupled with a coolant recovery tank, slight over-heating is not an issue. Heat exchangers can also be placed wherever, and it does not matter if the cylinder head is the highest point in the system.
As far as pressure caps are concerned:
1/ Less pressure can be used if the components exchange enough heat to keep the coolant temp under the boil temp. Boil temp will vary based on coolant used and pressure applied and ambient temp, etc.
2/ If the system components are marginal, then more pressure may save your butt/engine on a hot day. Again, based on coolant used and pressure applied and ambient temp, etc.
But this only works if your engine's water sealing can tolerate more pressure. Cosworth BD's are typically sensitive to this. The older Coopers Gasket BA0202 (as well as others) head gasket, made specifically for Cosworth, would usually leak from the packing in between the copper face and the steel base if the pressure was more than 7 psi. A "Bars Leak" capsule could save your butt, until a new head gasket could be fitted. I used to use a Fel-Pro "Print-o-seal" gasket to solve that problem. Then Cosworth caught on and used Fel-pro for their gaskets. I think most Cosworths now run Cometic gaskets.
3/ If the heat exchanger(s) is(are) too small in all environments, then you have no choice but to fit larger or more efficient heat exchanger(s) or better ducting or ??
Fordboy