Re: 1954 Packard Pacific 359 L8 radiator / blueprints #455036 and #446509

Posted by HH56 On 2020/11/24 17:31:53

7 psi was the postwar standard up until 53. At that time due to more reports of coolant being lost thru the overflow after a high speed run they went to a 12 and also made those retrofittable to the 51 and 52 models if needed. From 53 on it was mostly the 12 and 13 psi caps although a 7 was still available until 55.

They also changed thermostats with the change to the 12 psi cap going from the bellows type to the capsule type. It was found that as radiator pressure increased the bellows type did not open completely or even reliably at the stated temp. A larger diameter fan was also made available for warm climates or cars which had the coolant overflow problems. A larger radiator, multibladed fan, and a 12 or 13 psi cap was standard on AC cars.