Technical Radiator cap pressure for a 40 Ford(?)

THX

 

I have a stock radiator in my '40 w/283 Chev with upper inlet moved to center and outlet to lower right. I run a 4# cap. Water pisses out until it's happy at just the top of the core as viewed through the top opening. Runs 185 -190 with mech fan, no shroud.

vic

 

I don't believe pre WWII radiators were pressurized.

 

They weren't. You might get away with 4# if the rad and heater are in good shape. If you have a new rad, heater core, and rad and heater hoses you can go higher. I don't know how much pressure the stock water pump seals can stand.

 

Mine has a new core & top tank, but still has an original bottom tank. I run a 7# cap, and have run it as hot as 210 and not boiled over.

 

Will a modern, pressure cap even seat in the radiator to allow pressure to build ?