radiator cap pressure?
03-02-2006, 07:06 PM
#1
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radiator cap pressure?
1960, 350 engine, Dewitts direct fit radiator.
What size ie. lbs, radiator cap should i use? i had a 16lb on and a mechanic said i should use a 7lb.
What size ie. lbs, radiator cap should i use? i had a 16lb on and a mechanic said i should use a 7lb.
03-03-2006, 08:59 PM
#3
Former Vendor
One of the biggests myths is that caps either
A: Control pressure
B: Affect temperature
Pressure cap are simply relief valves. They limit the maximum pressure a system can see. They are NOT regulators...In other words they don't control or regulate the pressure. Pressure in the system is typically 3-5 psi all by itself. That does matter if you have a 7 psi or 70 psi cap. Now if something goes wrong in the cooling system, and the temperature rises, the pressure will rise with it. When it gets to the cap setting, it will puke out, limiting the pressure.
Yes, pressure changes the boiling point in coolant, it does not make a system run cooler. Many people install a higher setting cap to bandage another problem. The higher the pressure, the higher the boiling point. But the boiling point of a system with a 13psi cap is somewhere up in the 260 degree range, so would you want to increase that point to....what? If you car runs in the 180-220 range increasing the boiling point has no affect at all
A: Control pressure
B: Affect temperature
Pressure cap are simply relief valves. They limit the maximum pressure a system can see. They are NOT regulators...In other words they don't control or regulate the pressure. Pressure in the system is typically 3-5 psi all by itself. That does matter if you have a 7 psi or 70 psi cap. Now if something goes wrong in the cooling system, and the temperature rises, the pressure will rise with it. When it gets to the cap setting, it will puke out, limiting the pressure.
Yes, pressure changes the boiling point in coolant, it does not make a system run cooler. Many people install a higher setting cap to bandage another problem. The higher the pressure, the higher the boiling point. But the boiling point of a system with a 13psi cap is somewhere up in the 260 degree range, so would you want to increase that point to....what? If you car runs in the 180-220 range increasing the boiling point has no affect at all
03-03-2006, 11:08 PM
#5
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Originally Posted by Tom DeWitt
One of the biggests myths is that caps either
A: Control pressure
B: Affect temperature
Pressure cap are simply relief valves. They limit the maximum pressure a system can see. They are NOT regulators...In other words they don't control or regulate the pressure. Pressure in the system is typically 3-5 psi all by itself. That does matter if you have a 7 psi or 70 psi cap. Now if something goes wrong in the cooling system, and the temperature rises, the pressure will rise with it. When it gets to the cap setting, it will puke out, limiting the pressure.
Yes, pressure changes the boiling point in coolant, it does not make a system run cooler. Many people install a higher setting cap to bandage another problem. The higher the pressure, the higher the boiling point. But the boiling point of a system with a 13psi cap is somewhere up in the 260 degree range, so would you want to increase that point to....what? If you car runs in the 180-220 range increasing the boiling point has no affect at all
A: Control pressure
B: Affect temperature
Pressure cap are simply relief valves. They limit the maximum pressure a system can see. They are NOT regulators...In other words they don't control or regulate the pressure. Pressure in the system is typically 3-5 psi all by itself. That does matter if you have a 7 psi or 70 psi cap. Now if something goes wrong in the cooling system, and the temperature rises, the pressure will rise with it. When it gets to the cap setting, it will puke out, limiting the pressure.
Yes, pressure changes the boiling point in coolant, it does not make a system run cooler. Many people install a higher setting cap to bandage another problem. The higher the pressure, the higher the boiling point. But the boiling point of a system with a 13psi cap is somewhere up in the 260 degree range, so would you want to increase that point to....what? If you car runs in the 180-220 range increasing the boiling point has no affect at all
A higher pressure cap will allow the coolant to run hotter before boilover, so if you have a 15 psi cap and your coolant gets to 230 you still have over 30 degrees margin before the system starts puking coolant, which is when you should shut it down.
Even though early Corvettes had 7 psi caps, I don't think running a modern 15 psi cap will do any harm, and it will give you more margin.
I believe some new cars are running 21 psi caps, and I think NASCAR does to. This will probably raise the 50/50 glycol/water mix boiling point to at least 275, but I think NASCAR guys just run water so boilover would be lower. They usually start pulling tape when the temp gets to 230.
Duke
03-03-2006, 11:50 PM
#6
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Originally Posted by GO GIRL
Hey Tom,
When you gonna offer a group purchase (like your previous offer) on your awesome restoration radiators? Many of us are waiting.
When you gonna offer a group purchase (like your previous offer) on your awesome restoration radiators? Many of us are waiting.
I am also eagerly awaiting your offer for the resto rads!!!61rand
03-04-2006, 04:19 PM
#7
Former Vendor
Originally Posted by SWCDuke
Even though early Corvettes had 7 psi caps, I don't think running a modern 15 psi cap will do any harm, and it will give you more margin.
Duke
Duke
