Rad Caps??

I dont know if this will help or not but I'll say it anyway. For every 1 psi that is applied to the coolant system, the boiling point of the liquid will increase 3 degrees. So, If the boiling point of water under no pressure is 212 degrees, using a 10 psi cap would increase this by 30 degrees, or 242 degrees until the liquid boils. I would be a little leary of a lower pressure cap unless it is a pretty mild engine that doesnt make a lot of heat.