My '50 Olds has a BBC swapped in but still has the original radiator recored with a modern 4-row core. At the temp it runs I'd be more comfortable with a 14-16 psi radiator cap rather than the recommended 4-7 psi cap. I've always been told that the older tanks won't take that much pressure (they don't have the strengthening ribs like the newer ones). Has anybody run a higher rated cap on an older GM radiator? How high? Any problems?
I ran a newer cap on an older radiator. It wasn't good. Started leaking.. I had to go back to the old 6 lb. cap.
Yup-blew out an older radiator with a 12 lb cap. That's a bitchin Olds. 7 lbs is about all you can do with old radiator. If yours has a modern core and the original tanks, I would think you would be OK. Ask your radiator shop.
IT will work fine, the biggest problem was the header plate. If yur worried, split the difference and go inbetween. I ran a 14psi cap on my 38, original tanks with a new core, if you have seen the size of them 33-38 all have HUGE top tanks and it never worried that. Doc.
a friend ran a higher pressure cap on the expensive replacement radiator in his 56 chevy, the top tank ballooned. Modern radiators have much smaller tanks. The load on the tank from the pressure is figured by surface area times psi, so with a large flat tank surface you're looking at a heck of a lot of force trying to bend it outward.
The larger the tanks, and therefore more surface area, the less pressure it takes to "balloon" those tanks. I don't know if there's a rule of thumb of sorts. BUT, the cap recommendation's usually applied to those older tanks and not the newer core that's been installed. So, if they say 4lbs, I'd do it. I have a 4 pounder on my 38 Chevy and it spits water regularly, and needs to be topped off. A small price to pay for no problems. I have a recovery bottle that sometimes works with that recommended cap. So, it's a little less bothersome
I ran a 14lb cap on a new 4 row radiator in my 56 when a 7lb was recommended, it was not a good idea! my top tank separated at the front seam. Now I'm back to 7lb and everything is god.
My '53 Lincoln kept splitting top tanks on it's recently recored radiator. While at the salvage yard last week, which also has a radiator repair shop out back, the owner suggested I drop my 17 lb. cap down to a more reasonalble 7 lb. style. Early this week I drove the piss outa it to test his theory, got it nice and hot enough to allow a little bit out the overflow when it really got warm. Problem solved....................no more ruptured seams or core problems. I love my local salvage yard operator! I also like the '64 Sedan De Ville and the '53 Oldsmobile more door sedan he just got in for me. NEAT!
I'm with Groucho--I've had all types of caps on my 37 Ford--the 16 lbs caps always caused seam leaks.So now, I use 7 lbs caps--like Groucho says,I add water every now and then, but not radiator problems, and the runs cool. By the way--my 93 Chevy truck went thru 3 radiators in 4 years--plastic tanks/ aluminum core type--always leaking at the seams--so I dropped the cap to a 13 lb ---no more problems there now.
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