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Radiator cap question

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Old Apr 27, 2011 | 03:15 PM
  #1  
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Radiator cap question

The radiator I have is a stock(on the outside) 56 but I have it rebuilt with an additional row of tubes to help with the cooling. The radiator guy said to use a 4 pound pressure cap but since I am using a 351w engine my mechanic pals tell me that 4 lbs is not enough for this engine and that I need 12 lbs to keep the water in the radiator. The problem is that all the caps I can find which are the correct dimensions don't go over 4 lbs. I am sure someone has solved this problem before. Thanks for your help.
 
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Old Apr 27, 2011 | 04:11 PM
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Hmmm, I'm not much help regarding a stock radiator, but I have an aluminum Griffin rad with a 14lb. cap on my 351.
 
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Old Apr 27, 2011 | 04:20 PM
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Are you going to run an overflow tank? Are you running any other accessories, like AC? If not the 4lbs on should be fine, I run one on my 49 with a 350... I was told at one time that the Bronco or Dodge cap should work...
 
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Old Apr 27, 2011 | 06:17 PM
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My radiator is a stock dimension 4 core from Mid-Fifty. I use the recommended 7 lb cap also from them. I have no cooling problems with my 460 w/AC in CA.
 
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Old Apr 27, 2011 | 09:46 PM
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You need a better mechanic. Using a pressure cap on an old radiator is a good way to split seams, or other related damage. They weren't designed to be under 14lbs of stress. I had a 4lb cap on the stock 6 cyl. radiator I used with a 289, and I had no issues whatsoever. I don't know why anyone would tell you the SBF would blow the water out of the rad without higher pressure in the cooling system. That makes no sense at all.
 
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Old Apr 27, 2011 | 10:33 PM
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7lb cap on a 302 here
 
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Old Apr 29, 2011 | 11:57 AM
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OLD OLD OLD 4lb cap...mild 289 and I have had no issues. It spits once in a while if I get to rev happy...but my cap is probably close to 15 years old.
 
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