i have had a repeating problem with my rad that had a new core put in. it has been out of the car 3 times for leaks at the over the last 18 years. the last time i had it at the repair shop i was given info that for some reason i was surprised. maybe you all won't be. he told me that he way that the upper and lower tanks are attached, you should only use a 4 to 7 psi cap which he is telling me is stock for those old cars. maybe that will help someone.
from the service manual chapter 7
SSURE TESTING RADIATOR CAP
Select the short neoprene seal and metal adapter
from the kit, Tool (2-3499. Slip the seal on the tube at
the bottom of the instrument. Then attach either end
of the short adapter to the instrument. Dip the pressure cap in water and apply cap to end of adapter.
Working the plunger, as shown in (Fig. 7) bring the
pressure to 16 pounds on the gauge. If the pressure
cap fails to hold the pressure within a range of 14-17
pounds, replace the cap with a new tested cap.
The brass vent valve at the bottom of the cap
should hang freely. If the rubber gasket has swollen
and prevents the valve from hanging loosely, replace the cap. Do no
I've got nothing to back me up other than experience.
I'm glad V.R.D. posted the service manual specs.
1. I've run later model Chrysler caps (junk yard pull 16 PSI) on re-cored radiators for years with no problems.
My brother in law had his 1969 radiator re-cored and had to take it back to the shop several times.
It was a crappy job. Not neat at all on the tank solders.
They told him to run a lower pressure cap.
I called BS. It's brass and lead tin radiators.
What's the difference?
That might work but I think that's just a band aid for a weak radiator.
2. A mechanical engineer at work told me brass is the way to go.
I thought a lot of his opinions.
As far as I can see aluminum is cheaper and weighs less.
And may have some other "advantages".
.