Radiator cap, psi lb ?

[luigi164]

I'm looking for a new radiator cap so as usual I go to look at Rockauto.

I believe for a 383 2 barrel a 16 lb is the standard. But one is offered as 16 lb and the other as 16 psi...
Psi, lb...is that the same ?

Reason for my search is that my engine is running around 210 F.
At the moment I have a cap wich says 7 lbs ?? I've never noticed that but I think it's a little low ? The radiator however is not puking coolant at all.

Using my temp gun: upper hose reads 220 F, lower hose 180 F pointing at the waterpump reads 210 F.

Are these measurements ok?

 

[Wollfen]

Hi Luigi, 16 psi is 16lbs, the PSI is "Pounds per square inch" Hence a 16lb cap. And yes you should be running a 16psi/lb cap.

 

[luigi164]

Thanx Wolfen, I allready thought so but it's a bit confusing for us used to the metric system

 

[Wollfen]

Oh I forgot to mention, the boiling point of water at 16lb is 216 degrees Fahrenheit, so a less temperature than that it won't boil. The 50/50 mix of coolant raises the boiling point to 223 degrees Fahrenheit.

 

[65 500]

What thermostat are you running?

 

[luigi164]

I don't know, never pulled it out. But since I've installed aftermarked gauges and having a tempgun I started measurements (see my other thread)
Car runs fine and never had overheatingproblems or so. I thought the temp gauge should read about 180-190 F but it isn't. So now I want to know if the gauge is right.

 

[luigi164]

Finally I got the thermostat out. The bolts were so tight I was afraid to snap them off. So after a few days of using penetrating oil I got some movement and with slowly losing and tighten the bolts I finally got them out. Specially the right one, under that f%$#^ compressor was a pita to get out but...I've done it.
And the thermostat is.....180 F. According to the FSM it should be a 195 F.

So, I own the Newport for 10 years now and never had a problem with the coolingsystem that I'm aware off. The idiotlight (hot) has never lighted up.
Now with the gauges installed and the, in my opinion, high temperature, do I have to worry now?
Also asking, why did the previous owner used a 180F themostat ánd a 7lbs radiatorcap?
And, must I go to a 195 F and a 16lb ?

 

[CanCritter]

Finally I got the thermostat out. The bolts were so tight I was afraid to snap them off. So after a few days of using penetrating oil I got some movement and with slowly losing and tighten the bolts I finally got them out. Specially the right one, under that f%$#^ compressor was a pita to get out but...I've done it.
And the thermostat is.....180 F. According to the FSM it should be a 195 F.

So, I own the Newport for 10 years now and never had a problem with the coolingsystem that I'm aware off. The idiotlight (hot) has never lighted up.
Now with the gauges installed and the, in my opinion, high temperature, do I have to worry now?
Also asking, why did the previous owner used a 180F themostat ánd a 7lbs radiatorcap?
And, must I go to a 195 F and a 16lb ?

l would....just replaced rad cap for 70..16lbs

 

[65 500]

If it was my car I would put a 16 lb. cap on it, and put a new 180* thermostat in it.

 

[mr. fix it]

Oh I forgot to mention, the boiling point of water at 16lb is 216 degrees Fahrenheit, so a less temperature than that it won't boil. The 50/50 mix of coolant raises the boiling point to 223 degrees Fahrenheit.

I have to disagree on your math here
At 16lbs the boiling point is much higher than 223f
Normal boiling point for water would be 226
50/50 coolant takes it much higher
Check out the link here

https://durathermfluids.com/pdf/techpapers/pressure-boiling-point.pdf

 

[65 500]

I have to disagree on your math here
At 16lbs the boiling point is much higher than 223f
Normal boiling point for water would be 226
50/50 coolant takes it much higher
Check out the link here

https://durathermfluids.com/pdf/techpapers/pressure-boiling-point.pdf

I agree with the first part of that, but those charts are giving different boiling points for the same pressure.

 

[mr. fix it]

I agree with the first part of that, but those charts are giving different boiling points for the same pressure.

I'm looking at this on an iPhone screen but it should be due to different coolant mixes

 

[65 500]

For example:

 

[Polara_500]

Just a little word of caution, many folks have been known to install a lower pressure radiator cap as a fix for a cooling system with questionable integrity. I had a radiator shop recommend I do that on an old chevy truck I had or they wouldn't guarantee the rad repair. (They insisted a 7 lb cap was max.) So it is possible that if you raise the pressure you may find a weak point in the system.

 

[Wollfen]

I have to disagree on your math here
At 16lbs the boiling point is much higher than 223f
Normal boiling point for water would be 226
50/50 coolant takes it much higher
Check out the link here

https://durathermfluids.com/pdf/techpapers/pressure-boiling-point.pdf

That link is totally self contradictory, in the writing above the table it states that water boils at sea level at 212F which is 14psi pressure ( equal to one atmosphere of pressure) Yet the table below it says that at O psi pressure it boils at 212F, but O psi pressure would mean no air pressure which of course doesn't make sense.

 

[Wollfen]

I used this site for pressures,
Water - Pressure and Boiling Points

 

[mr. fix it]

That link is totally self contradictory, in the writing above the table it states that water boils at sea level at 212F which is 14psi pressure ( equal to one atmosphere of pressure) Yet the table below it says that at O psi pressure it boils at 212F, but O psi pressure would mean no air pressure which of course doesn't make sense.

I Think it would be understood to mean no added pressure past typical atomospheric pressure...

 

[300rag]

That link is totally self contradictory, in the writing above the table it states that water boils at sea level at 212F which is 14psi pressure ( equal to one atmosphere of pressure) Yet the table below it says that at O psi pressure it boils at 212F, but O psi pressure would mean no air pressure which of course doesn't make sense.

If you compare your chart with that one, you can see that the first one is actually a pressure differential from sea level. The temp at 15 PSI on the one chart corresponds to 30 PSI on yours. Their 24 14 PSI corresponds to 24 14+15 or 30 PSI on your chart.

 

[Wollfen]

I Think it would be understood to mean no added pressure past typical atomospheric pressure...

The fact that the table also says water boils when at 20 psi at 260F then next says it boils at 272psi shows me someone didn't pay too much attention to making these tables and they cant be taken as gospel, they are not reliable.

 

[Wollfen]

If you compare your chart with that one, you can see that the first one is actually a pressure differential from sea level. The temp at 15 PSI on the one chart corresponds to 30 PSI on yours. Their 24 PSI corresponds to 24+15 or 30 PSI on your chart.

24 + 15 is 30? You need to go back to school.