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Thread: Radiator cap

  1. #1
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    Radiator cap

    Is it important to have a 13 PSi cap on a 289 engine? What is the purpose of one. Why not a 6or 7 psi?

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    The higher pressure just allows...higher pressure within the system before it blows out on the ground.
    Presumably a slightly higher temperature before boiling.

    Depending on the outside temp., sure you can use a 6 or 7psi cap without problem. The higher pressure cap "might" become a good thing if the ambient temp. is over 85 or 90 degrees.

    Mike

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    The higher pressure raises the boiling point. It may be useful, on Avanti's, in swelling out dents in the reservoir tank. The engine shouldn't be running hot enough to need such a high pressure system. I use a 7 lb cap and a coolant recovery system. I can see it over flow into the system's reservoir, and draw coolant back into the engine when it is shut down. This should remove air pockets and make the system more efficient.
    It also prevents puddles of coolant in the driveway. I understand ethylene glycol tastes like pumpkin pie, and causes symptoms like a heart attack. Pets and wild life lap it up.
    A functioning recovery system, with a low pressure cap, is an improvement over the high pressure system.
    Mike M

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    The boiling point of water, water and coolant, goes up as the pressure increases. Water boils at 212 degrees +/- depending on atmospheric pressure. The higher you can make that temperature, the longer the coolant remains in a fluid state, which allows the best heat transfer and best circulation. As soon as water becomes steam it alters the heat transfer ability and circulation of the coolant. The engine itself will run more efficiently at higher temperatures, but that needs to be moderated to keep the internal parts from damage. A low pressure cap will work as long as the boiling point is controlled by it. Add lots of extra fluid to absorb the heat and lots more radiator surface to dissipate it and the engine will run at a cooler temperature--just not as efficiently. Miss the balance between all the variables, and watch you coolant boil away as steam and pour in some more to replace it before the engine seizes from excess internal temperatures. The older cooling systems could work at lower pressures, less power, less internal stress, less efficiency, huge radiators, a lower boiling point wasn't a problem-most of the time.

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    This has been a great help. Thank you for the advise.

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    Speedster Member bensherb's Avatar
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    The coolant's boiling point is raised approximately 3 degrees for each pound of pressure it's under. So if your coolant boils at 212 degrees at atmospheric pressure it will boil at 233 degrees with a 7 LB pressure cap, or at 254 degrees with a 14 LB cap.

    So if you drive in high ambient temps, or have a tight/fresh engine, or one that makes a lot of heat for another reason, a higher pressure cap/cooling system may help keep from it overheating. A higher pressure cap can also let you get away with a cooling system that is smaller than might otherwise be able to do the job.

    As mentioned by Mike, above; I also run a closed cooling system, which also increases cooling system efficiency.

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    President Member TWChamp's Avatar
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    The high pressure cap is also why you must stand clear when removing it. The sudden release of pressure will turn your radiator tank into Old Faithful.

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    Speedster Member colt45sa's Avatar
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    Quote Originally Posted by Daytona View Post
    Is it important to have a 13 PSi cap on a 289 engine? What is the purpose of one. Why not a 6or 7 psi?
    NO~! Older radiator design with top and bottom tanks were not designed for high pressure caps. There is a distinct probability that the higher pressure will cause the tank and core to separate, then you've got a problem.

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    President Member 52hawk's Avatar
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    In my opinion,if your 289 Studebaker radiator won't handle 13 lbs,you need a new radiator. Using a lower pressure cap is a band aid for a questionable cooling system.
    Oglesby,Il.
    Buy a smart car,I need your gas.

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    Yes; It is physics 101. 1 ATM pressure raises the boiling point . Studebaker used 13 psi caps from 1956 on.

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    Silver Hawk Member JoeHall's Avatar
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    Quote Originally Posted by 52hawk View Post
    In my opinion,if your 289 Studebaker radiator won't handle 13 lbs,you need a new radiator. Using a lower pressure cap is a band aid for a questionable cooling system.
    Agree, I have always ran 13-14 PSI caps on Studes. A year or so I picked up a 7 PSI at an SDC meet, but really do not know what I was thinking. Pretty sure 13 PSI is what is called for with Studes.
    Way too many folks trying to run their Studes with radiators that have pretty much rotted away. Might be safer to run those with cap loosened, so zero pressure builds.

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    Joe; I really don't like sitting on the side of the road waiting for the tow truck 'cause I was too cheap to clean and pressure check or re-core the radiator. That should come before the bling and those idiotic wheels. You can buy a new Al radiator for less than one ugly wheel. If things are working properly you ought to be running 160 to 180 degrees and you don't need the pressure but I also like a coolant recovery system; they purge air from the system and that helps combat corrosion. They won't work in a non-pressurized system

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    Silver Hawk Member JoeHall's Avatar
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    Quote Originally Posted by Jeffry Cassel View Post
    Joe; I really don't like sitting on the side of the road waiting for the tow truck 'cause I was too cheap to clean and pressure check or re-core the radiator. That should come before the bling and those idiotic wheels. You can buy a new Al radiator for less than one ugly wheel. If things are working properly you ought to be running 160 to 180 degrees and you don't need the pressure but I also like a coolant recovery system; they purge air from the system and that helps combat corrosion. They won't work in a non-pressurized system
    I agree. Cooling system is more important than cosmetics, to me. Each of my three Hawks has a special cored radiator, with original tanks still in place. They cost about $750 each, about five years ago. Its not that I like spending money, its just that I accept that sometimes it is necessary. The radiators are equivalent to a 5-core, if Studebaker had made such a thing back in the day. All three cars run nice and cool, even with AC in the summertime. All three cars also have a 195 thermostat, which works well with an efficient cooling system

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