Radiator caps...what rating to use?

[Edbert]

Standard caps are either 14 or 16 pound caps right? I was looking around and see high-performance caps rated at 20# and even some as high as 28#!

So, the difference determines how much pressure can build before it releases, thus allowing higher temperatures? What is the benefit or detriment of getting a higher rating?

 

[iskwezm]

A higher pressure cap will raise the boiling point of the water, but too high will stress your cooling system if its not up to the increased pressure.

 

[69gmachine]

Stick with the 14# cap. You'll probably just create a leak somewhere because the cap won't vent.

 

[bnickel]

stock mustang caps can go as low as 9lb depending on the application but most use a 13lb one. i wouldn't personally go any higher than 16lb.

 

[66 Restomod]

Just wondering, is there a difference on cap pressure if a non-stock overflow tank or catch can is added? I'm thinking of adding a catch can next to the radiator on my 66, not sure if I'll need a new cap...

 

[Tim65GT]

Just wondering, is there a difference on cap pressure if a non-stock overflow tank or catch can is added? I'm thinking of adding a catch can next to the radiator on my 66, not sure if I'll need a new cap...

No, they have two independant purposes. Just route a hose from the overflow tube at the neck to the new catch can that will allow the coolant to siphon back into the radiator as it cools.

 

[Edbert]

Yeah, the neck has the outlet not the cap. The pressure rating on the cap determines at what point fluid is released into the top of the neck.

 

[bnickel]

the caps are different though. the one with a catch can will have 2 rubber seals one without will only have one seal. these days you'd be hard pressed to find a cap that doesn't have 2 seals though.