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I need to get a radiator cap – just to have on the car to run until I can get a correct one.

I guess it will be something off the shelf from the local parts shop.

What specifications to I match up in terms of dimensions? And I figure I get something that's equivalent to 7 lbs pressure?
 

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I need to get a radiator cap – just to have on the car to run until I can get a correct one.

I guess it will be something off the shelf from the local parts shop.

What specifications to I match up in terms of dimensions? And I figure I get something that's equivalent to 7 lbs pressure?
They repop the AC RC-1 549 7#..check ebay,Danchuck,Ecklers
 

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If its a standard radiator, you can get a 7 lb at any parts store. I got one at AutoZone. Don't go over 7lb, you could blow your heater core, ask me how I know.
 

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Discussion Starter · #7 ·
If its a standard radiator, you can get a 7 lb at any parts store. I got one at AutoZone. Don't go over 7lb, you could blow your heater core, ask me how I know.
Thanks. I got one just before from my local parts supplier – 2 1/4" rated to 7 lbs.
 

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Cause I put a 10 lb pressure test on mine, and it blew my radiator core out in 30 minutes. Oh, I forget, ya'll don't do in pounds. What does 7 pounds translate to?
I have a 9lb one on mine with no problems. Stock rad and heather core
 

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Junk heater cores and junk radiators leak. A replacement heater core that is manufactured correctly can be run with a 16 psi cap. There is nothing structurally wrong with a stock style 55-57 heater core as far as running higher than a 7 psi cap.

An old corroded one is going to leak pretty soon. Maybe it blows sooner with a high pressure cap, but that's a matter of weeks or months not years.

I don't know how these myths get started. Well actually I do. You just have to think straight.
 

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I used one off of a Farmall tractor on the factory radiator of my 55 while I was breaking the cam in and even made a few test drives with it.
 

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Rick L . I understand what you mean I think. Your saying you can run a 16lb cap if the rad and heater core are good... and then you say Use a 7lb cap I'm confused.... Peter
Everything I've read said your rad will probably be OK or at least bulge your tanks, but the stock heater core will not be able to take that.

it's up to you I guess :anim_25:
 

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They're putting 16lb rad caps on the new garbage aluminum rads with plastic tanks , so I guess I'll leave the 14 psi cap on my 57 year old radiator for one more season . I changed out the heater core 2 years ago , and see no signs of any "tank bulging" or other fantasy problems . The system was designed for a low-pressure cap , but was built with a huge safety margin . The brass/copper radiator technology was excellent in 1955-57 , but too expensive to manufacture now . Try not to listen too much to the naysayers ; like Rick said , junk is junk . Good radiators and heater cores can take the 14psi , no problem ; the weak old corroded ones can't . Be safe...Bob.
 

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My core was not junk, but it was old and didn't appear to be corroded. Been running like that for years, and wallah, put a new cap on and it blows. I guess its kind of like me, if you put too much pressure on this old man, I will probably blow out at the seams. I guess to each his own. I will continue to run the recommended 7 lb cap.
 

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Rick L . I understand what you mean I think. Your saying you can run a 16lb cap if the rad and heater core are good... and then you say Use a 7lb cap I'm confused....
No I said you don't have to use a 7 psi cap if the core is in good shape. At least that's what I meant.
 

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The way I look at it is they were 7lb and not 16lb for a reason. Like I said, I have a 9lb and I'm pushing it with my untouched stock heater core.
 

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Yes but one reason was that the radiator and heater core were manufactured with 50s technology. 21st century replacements are better unless you buy them from China. The heater core should be inherently better because it's smaller. Plus the manufacturing integrity of everything was improving rapidly through the 40s/50s/60s.

Remember that radiator caps were commonly 14-15 psi by the mid 60s with no real change in radiators or heater cores. As much as anything, they just realized you could do it and that there were benefits from doing it. I think hoses were at as much risk as anything back then. Hoses are MUCH better now.
 
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