Quote:

So I want a bottle with a vent on the top and a "recovery' type cap. The bottle I was looking at (the one that might fit) is 20oz capacity. I worry that a full to the brim radiator will discharge more than 20 oz and spit coolant out the vent. Valid concern?

Also not sure about my cap. I ran the car with a Stant lever cap (model 331) and when I shut it down a bunch of coolant puked out but the upper radiator hose was not hard (no pressure) Maybe it had relieved the pressure before I squeezed the hose? Not sure.



20oz capacity is plenty. Only a high-schooler pukes more than that.
Caps vary in pressure...around 7 pounds is light, around 15 pounds is 'heavy'. Higher pressure raises the boiling point, but it also stress-tests the radiator more.
Again---you want the cap with the button, you can get the lever too.
MOST caps nowadays ARE coolant recovery, with the button.

On my 70'cuda I am using the windshield washer bottle as the coolant tank--works perfect.