Originally Posted by JohnG
The lower the pressure the better.... less stress on that cheesy expansion tank on the top! Make an overflow bottle for inside the engine compartment (for non-show times) and catch anything that comes out so you're not dumping toxic stuff into the street.
Well put and this is what I found out. My expansion tank was leaking at the seam so I brought it to the radiator shop for repairs. The repairman told me that he would recommend a 10lb cap because of the typical temperature fluctuations in the radiator. Mine will easily see 210 on the gauge at a stop light in the summer, but climb back down to 180 when I get moving (i have a gauge). Sure, it will spit it out, but if you have an overflow it will eventually suck it back in. I HAD a 13lb cap.