That is interesting, as ive been reading a lot about how 50s to mid 60s radiators were built to use a 7lb cap,
The higher rated caps affect gaskets/plugs on ur engine as well...not just the radiator!
Was running a 7 lb before our recore. Switched caps with our other dart for 13. Now running 13 on new core and 7 on rad with small leak.
There are several schools of thought on the issue of more pressure = cooler running temps, etc.. You can run either but the 7lb will relieve pressure alot sooner than 13, so...... Use em how you need em!
Main thing though is to be sure you run a cap for an overflow system if you have an overflow bottle. Otherwise you will have hose collapse, overheat issues etc...
10-4!
