I have a '40 Chev Coupe with original radiator and a 350 V-8 engine, 350 trans., and A/C.
I have been running a 15-17 # cap on the rad. as a closed system with overflow tank for almost 30 years without a problem. Never blew a hole in the rad.
Use the vent tube to run hose to overflow tank as modern cars do.
Just my Thoughts,
Walt
