Kim72

Currently running 16 psi Stant cap that is looking a little ratty. Plan on replacing it. Is there any advantage in running any different pressure? Big block, non a/c, car c/w Dewitts rad. Usually runs at 180 degrees. Can get up to about 220 in heavy traffic on a hot day.

bashcraft

The system was designed for 16 psi. Sounds like you're trying to fix something that's not broken.

Alan 71

Hi K72,
I believe the original 70-72 cooling systems, both sb and bb, were designed to use 15# radiator caps.
I believe the Dewitt's radiators are designed to use 15# caps too.
Regards,
Alan

0Tom@Dewitt

I get asked this question daily and most people stress out over the decision when it really doesn't matter. Remember "boiling" is not "running" temperature and this is a level that you should rarely ever see. If you "boil" over, it is most likely due to a completely stuck (closed) stat or a water pump failure or something like that.

A coolant mixture of 50/50 has a boiling point of 223 degrees. Pressurizing the system will raise the boiling point by 3 degrees for every 1 psi on the pressure cap. A system with only a 7 psi cap will have a boiling point of 244 degrees and that should be a temperature that no system should ever reach. Typical pressure caps are either 13# (262 F) and 15# (268 F) and six degrees difference is nothing to lose any sleep over. Sometimes people will overfill the system and mistake expanding fluid for boiling fluid and think they need a higher pressure cap to prevent the coolant from escaping. After the coolant has exhausted to the driveway and the engine cools down, they will re-fill the system and continue the cycle over and over.

Wee

Been there done that...But only once.

Brian