What lb radiator cap 347 sbf

[Daryl]

Was sent their accompanying 19lb cap when I bought the Mishimoto aluminum radiator but as I’m spitballing possible reasons I: (1) had a little trickle leak after running it harder than usual; and (2) fluid cold always drops down to the bottom of the filer neck?? Where does it go, the overflow tank? Level seems the same there as always.
I Goggled “what lb radiator cap for 347 SBF” and it came up 13-16lb cap. Is 13-16 correct for a METAL rad and 19lb for aluminum?

 

[96blak54]

Good question! I would have simply unknowingly used 13-16lb cap, but now i question.

 

[Mustang5L5]

I run a 16lb cap.

The only advantage to running a 19lb cap is you raise the boiling point of the coolant. With a 16lb it's around 270 degrees. With a 19lb it's around 280 degrees.

The downside is higher system pressure, and increased stress on seals and such.

 

[Daryl]

Maybe there’s some merit to me going to a 16lb cap because yesterday when I took the car back to get smogged it popped a pinhole leak in the 2-pc (replacing with 1-pc) water pump hose and overheated. This is the 2nd visit for smog check. First didn’t pass (gross polluter) so spent $400 at the tuners to reset calibrations, etc.

So yesterday I limped it over to my mechanic for a new hose. Too afraid to chance it home at 230* water temp.

 

[Daryl]

I run a 16lb cap.

The only advantage to running a 19lb cap is you raise the boiling point of the coolant. With a 16lb it's around 270 degrees. With a 19lb it's around 280 degrees.

The downside is higher system pressure, and increased stress on seals and such.

Is that on a metal or aluminum radiator? If aluminum, any issues?

 

[CobraRGuy]

Is that on a metal or aluminum radiator? If aluminum, any issues?

Another upside of higher pressure is the radiator will transfer more heat. That's probably why Mishimoto supplied it.
This principle has been known for a long time and is used in HVAC design a lot.
A downside is more stress on your hoses.
I too use a 16lb up on the degas bottle, which is what it came with.
The cap on the radiator itself only seals around the outside with no pressure mechanism, and the hose connected there directs gas to the degas bottle.
The lower hose has a Tee. This is where any air bubbles need to be trapped and directed up in order to prevent them from getting to the pump where any bubbles at all can disrupt the water flow.


CobraRGuy