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By 54 country squire - 12 Years Ago
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hello, I have a question for the y-block experts. I have been unable to find pressure rating specs for my 239 y. it currently has a 7lb. cap on it. the reason I am not sure this is correct is I also have a 55 merc w/ a 56 312 y in it and it has a 13lb cap? did the pressures of the y-blocks vary over the years? when I run the 239 and it gets hot it does not seem to build pressure, you can remove the cap as if it was cold. I was always told the right lb., cap is critical to the cooling system. any thoughts or opinions? thank you to all that have responded in the past, your input is very helpful, doug.
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By oldcarmark - 12 Years Ago
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If there is no pressure released when you remove cap hot(you shouldn't be able to remove cap without a great deal of caution when hot) than perhaps the cap is defective or the wrong cap.The Parts Catalog lists both 7 and 13 lb caps for 55 and 56.It has been suggested in view of the fact these rads and heater cores are older in many cases,its a better idea to use the 7 lb cap.Of course if you have a new rad and heater core a 13 lb cap will raise the boiling point of the coolant.
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By GREENBIRD56 - 12 Years Ago
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So if the radiator top tank is (for instance) 5 inches W x 30 inches L the upper area is then 150 sq inches. Total force of 1,950 pounds at 13 psi and a perimeter of 70 inches relates to a load of 28 pounds per lineal inch of seam. At 7 psi it drops to 15 pounds per inch. When I asked the local "desert radiator" repair guys they said use the recommended 13 psi cap (T-bird manual). Boiling temperature goes up by roughly 2.5 degrees per psi so an additional 15 degrees over the 7 psi cap.
I'm sure they are relating to system (and component parts) in good shape - but that sort of load difference on a tank solder joint shouldn't be the difference between success and failure..........right? 
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