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Old 08-31-2012, 04:55 PM   #6
Old Henry
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Location: Orem, Utah
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Default Re: rad. pressue caps.

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Quote:
Originally Posted by dick lyons View Post
what would the consequences of useing 13# cap?
On my Pike's Peak trip I put on a 10# cap to keep the water in at high altitudes. The consequence was that water started squirting out of the hoses past the hose clamps. The system is just not made to hold that much pressure.

Increasing the pressure of the water raises its boiling point such that the engine will get hotter before boiling the water out. Here's how it works:

In your state all elevations are close to sea level. At sea level of c. 15 psi water boils at 212 deg. So, if you had no radiator cap the water would boil out at that temperature. Adding a 4# radiator cap raises your boiling temperature to 225 deg. and a 13# cap raises it to 245 deg. So, as you can see, the higher the pressure of the water the hotter it can get before boiling out. That's about it other than where the old system designed for 19 psi (sea level psi of 15 plus 4# cap) is going to blow with 27 psi in it.

You may have noticed that modern engine temperature gauges don't redline until 260 deg. That's because modern engines have a 15# cap that keeps water in to 250 deg.
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